Key notes on Geography of India in the Aryan Era
The Godwin system derives its name from the kingdom of the Gonads, an ancient tribe of central India. The rocks of this system were deposited in a series of large rivers of lake basins which later sank along trough faults among the ancient rocks. The Godwin rocks are mainly developed along the Deodar, the Narmada, the Godavari and the Mahanadi valleys. The rocks of this system are rich in coal, iron ore, copper ore, uranium and antimony.
Triassic system is well-developed in the northern Himalayan zone from Kashmir to Kumauni. It comprises black limestones with shale intercalation and quartzite’s.
Jurassic system occurs in the Himalayan region Spite, Kumauni, Kashmir, Hazard in Kutch and Rajasthan.
The Cretaceous system was one of the most widely distributed systems in India occurring along the Narmada valley and in the central parts of the peninsula.
The Deccan Traps:
The volcanic activity takes place in the peninsula from the end of the Cretaceous till the beginning of the Eocene period. There was an immense pouring of basaltic lava which spread out far and wide as nearly horizontal sheets and filling the irregularities of the pre-existing topography. These lava deposits are found in Maharashtra, Saurashtra and in Madhya Pradesh called Deccan Trap region. Hills of the Deccan Trap are noted in the Sapura area and in Reba.
Dykes are numerous in the Traps. This region consists of quartz, agate, amethyst and calcite. The weathering of the volcanic rocks of this region give rise to the formation of black soil which is very fertile for the production of cotton, groundnuts, castor seeds and wheat.
The Tertiary System:
The tertiary system in India is subdivided according to the phases of the .Himalayan upheaval; Tertiary rocks are well-developed in the extra peninsular region in India, from Kashmir through the Himalayan foot hills to the Brahmaputra gorge in the extreme north-east of Assam.
In peninsular India the rocks of this period are found in Saurashtra, Surat-Bharuch, Cambay region and Kerala on the west coast and from southern Tamilnadu to Orissa (Godavari delta, Pondicherry, Cauvery basin, south Arco, Thanjavur) in the east coast.
The Eocene to Middle Miocene System:
The fossiliferous deposits of the upper part of the Eocene together with the Oligocene are present in Gujarat, western Rajasthan and Assam. In Assam, Eocene is represented by limestone’s and coal-bearing sandstones of Jacinta series in the southern and eastern parts of the Shilling plateau. Such deposits also occur in western Rajasthan and in Gujarat. Coals, limestones are the important minerals which occur in this system.
The Sixalik system covers long stretches in the extra-peninsular India along the foot of the Himalayas from Hardwar to Brahmaputra valley. The rocks are made up of sandstones, grits, conglomerates, clays and silts and contain large number of fossils.
The Pleistocene and Recent formations:
There was an onset of Ice Age in India during the Pleistocene period. Evidences regarding glaciation are found everywhere in the Himalayas. In Kashmir, four or five periods of glaciation with three inter-glacial periods, have been distinguished. Pleistocene and recent deposits occur in the Narmada, the Tapti, Purina river valleys and along the upper Godavari and upper Krishna valley.
The most important Pleistocene geological formation is the Indo-Gang etic alluvium filling. The older alluvium i.e. Banger dark in color contains carbonate of lime covering the higher ground. The new alluvium i.e. Khaddar is found near the present course of the rivers. It is light-coloured and poor in calcareous matter. The Pleistocene and recent deposits contain gravel, clays, peat marshes and sand.