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Gondwana Flora And Fauna – Geology Notes For – W.B.C.S. Examination.
গন্ডোয়ানা ফ্লোরা এবং প্রাণিকুল – ভূতত্ত্ব নোট – WBCS পরীক্ষা।
The name ‘Gondwana’, suggested by H. B. Medlicott (1872), is derived from the ancient tribal Dravidian Gond Kingdom of Madhya Pradesh ruled by Rani Durgabati during the reign of Akbar the Great. Later the term ‘Gondwana System’ was published by Ottokar Feistmantel (1876), comprising of continental rock formation with coal seams and fossil plants and animals of the Upper Palaeozoic as well as Mesozoic Eras.Continue Reading Gondwana Flora And Fauna – Geology Notes For – W.B.C.S. Examination.
Other scientists discovered similar continental rock formations with coal seams and fossils from faraway continents of the Southern Hemisphere like South America, South Africa, Antarctica, Australia, Madagascar and New Zealand. Thus, the concept ‘Gondwanaland’ (Fig. 1.98) was introduced by Edward Suess (1885) which was originally conceived by Blanford (1875).
It is believed that the Gondwana Era began after the second major period of earth revolution, the Hercynian Revolution during Upper Carboniferous. The Gondwanaland lasted up to the beginning of the Cretaceous when the third major revolution of earth i.e., the Alpine- Himalayan Revolution took place.
This gave rise to the concept of two supercontinents by Du Toit (1937), one forming the Northern continental mass, the Laurasia and the Southern continent Gondwanaland, separated by the great equatorial Tethys sea. Thus, the single landmass, Gondwanaland, existed, showing a clear floral continuity ranging in age from the Upper Carboniferous to the beginning of the Cretaceous, from bottom to the top.There was free and easy migration of plants and animals in this land mass, exhibiting similarity in floral composition and climatic conditions. There was several local minor revolutions of earth that changed the pattern of flora or fauna of the region in some periods. Though, these minor revolutions did not affect the whole landmass and many of them must have been localised.
Gondwanaland existed from the Lower Permian to the Lower Cretaceous with a span of 225 m.y. The Gondwana system is comprised of continental deposits of conglomerates, sandstones, shales and coal measures of mainly fluviatile (river) and locustrine (lake) origin. Recent works also indicate the presence of some marine intercalations in the Gondwana sediments of central and east coastal India.
The sediments were deposited in trough-like basins, bounded on either side by older Archaean rocks which endured faulting. Archaean rocks protected the Gondwana deposits from denudation and thus preserved the sediments in their original horizontal stratification. There is a striking homogeneity of Gondwana sediments with a uniform alteration of sandstones and shales bearing coal seams.The Gondwana rocks are mainly distributed in major river valleys of Peninsular India. These are —
(i) Damodar valley,
(ii) Sone-Mahanadi valley, and
(iii) Wardha-Godavari valley.
A few exposures also occur in the Eastern coast (e.g., Cauvery, Palar, Krishna-Godavari and Orissa), Western Rajasthan, Saurashtra and Kutch.In the extra-peninsular, some detached outcrops are found in northern India such as Punjab Salt Range and Kashmir; and also in the sub- Himalayan regions of Sikkim, Bhutan, Arunachal Pradesh and Assam. The extra-peninsular outcrops have been subjected to metamorphism, showing very poor fossil content.
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