Gondwanaland

Inscriptions of Nature investigates the historical processes through which the past became naturalised. It explores how the deep past of nature became pervasive in historical imagination. In doing so, it challenges the way we have imagined the relationship between nature and history. It argues that how we think about the past became indelibly stained by our ideas of the deep history of nature, landscape and geography in the nineteenth century. The book studies these processes along the banks of Yamuna and Ganga, in the Himalayan crests, in the deep ravines and forests of central India, and in their associated myths and legends. The book shows that due to this naturalization of the past, geomythologies acquired powerful naturalised motifs in India. This became especially vivid and articulated in the nineteenth century when myths were linked to specific geographical sites and geological phenomenon. In other words, myths appeared real as they were inscribed into the landscape and thereby into the deep past of the nation.

The debate on the Gondwana stratigraphy in the Pranhita-Godavari and Johilla valley basins against that of Damodar Valley and many other Gondwana basins is persisting for more than a century. The intra-cratonic Gondwana basins host early Permian to early-mid Jurassic sediments. The Gondwana lithostratigraphic units can be structured broadly around a composite sequence of four representative lithostratigraphic units, like the glaciogene Talchir, the carbonaceous shale and coal-bearing Damuda, the feldspathic sandstone and red-mudstone bearing the Panchet, and the hill-forming, feldspar-poor, quartzarenite and variegated claystone bearing the Supra-Panchet. These lithostratigraphic units are referred to here as units A through D. On the other hand, the unit known as the ‘Kamthi formation’ has late Permian to early Jurassic dual and mixed-up bio-and lithostratigraphic levels. Each of these lithostratigraphic units corresponds to formation or group rank. These Gondwana sediments derived from granitic source were deposited largely in fluvial basins involved in block-faulted half grabens. The sedimentation coincided with the global climatic cycle as it was changing from an icehouse state in the Late Paleozoic to a greenhouse state in the Mesozoic. The influence of changing climate over the sequential development of lithostratigraphic units also provided an additional stratigraphic tool. The unit D overlies lithostratigraphic units A through C with a distinct unconformity. However, in the Pranhita-Godavari and Johilla valley basins some workers recognized sequences of two C and D lithostratigraphic units. Our study instead, revealed the presence of only one each of lithostratigraphic units C and D in all the Gondwana basins. Improper definition of the Kamthi formation applying over reliance on mega plant-based biostratigraphy, and its dual stratigraphic setting created many problems. To resolve these, a Field Seminar was organized covering the Kamptee, the Satpura, the Pranhita-Godavari valley and the Johilla valley basins (latter being a part of Sohagpur coal basin). Study of critically chosen and representative sections in all these basins established unified Gondwana lithostratigraphy in the peninsular India.

0. Abstract                               1
1. Introduction                               2
2. Paleomagnetic constraints on the Neoproterozoic supercontinent  3
2.1 1100–900 Ma: Laurentia and Baltica               3
2.2 1100–900 Ma: Amazonian craton (AC) and Baltica       3
2.3 1100–900 Ma: Kalahari craton               5
2.4 1100–900 Ma: Congo–Sao Francisco (CSF) craton       5
2.5 1075–990 Ma Siberian craton                       5
2.6 India 1100–1000 Ma                               5
3. True polar wander?                       5
4. The breakup of Rodinia: 800–700 Ma               5
5. 580 Ma and younger reconstructions               7
6. Conclusions                             7

1998.03 During the past 20 years, as a result of careful revisions and refinements, the broad plate tectonic, palaeogeographic, palaeoclimatic, and biogeographic history of Gondwana has become well known. The supercontinent of Gondwana was wrought during the Pan-African collisional event (600 Ma ago) and remained intact for over 400 Ma. During that time interval it crossed the South Pole, joined the northern continents to form Pangaea, and split apart in 3 distinct phases beginning in the Early Jurassic and ending in the Late Cretaceous. So what else is new? What more is there to know? Lots.
Though the broad outline is well known, important questions remain unanswered. Regarding its formation, 'How many continents were involved?', 'What was the exact timing of collision between these pieces?', 'What was the polarity of subduction?', 'When, exactly, was the process finished?'. 'What, if anything, did the formation of Gondwana have to do with the Vendian Ice Age, or the diversification of metazoans?'.
Gondwana was largely intact, and traversed the South Pole during the Palaeozoic, however, the details of its Palaeozoic history are not well known. For instance, 'What initiated subduction along the Tasman-Transantarctic-Cape Trend?'. 'Does palaeomagnetic and palaeoclimatic eyidence from Gondwana support a period of rapid True Polar Wander during the Late Precambrian-Early Cambrian?', 'What path did Gondwana take as it crossed the South Pole? Was it slow, steady, or rapid with loops and twirls?'. 'How extensive was the Late Ordovician Ice sheet?, Did it really stretch from Cape Town to Yemen?', and 'Can we make sense out of the history of terrane accretion in southern South America and eastern Ausutralia?'.
During the Early Palaeozoic, the Cathaysian and Cimmerian Terranes seemed to be associated with the Indo-Australian region of Gondwana, 'Where exactly were they located?', and 'When did they rift away from Gondwana?'. Biogeographically speaking, 'What does the distribution of the earliest fossil fish tell us about Siluro-Devonian palaeogeography?', 'When did the first terrestrial vertebrates arrive in Australia?', and 'Where did they come from?'.
The Early Jurassic through Late Cretaceous break-up of Gondwana is well documented by geological, tectonic, and marine geophysical data, however a few nagging questions remain. 'Are the Karoo rifts a precursor to Gondwana break-up, or an earlier, unrelated event?', 'What was the fit of the continents that comprised eastern Gondwana?', 'Was it a loose fit or a tight fit?', 'How exactly does India fit against Madagascar?', 'What went in that gap between northwestern India and Arabia?', 'What rifted away from northwestern Australia?', 'Was there a large chunk of continental crust north of India (Greater India)?', 'Where did it go?'. Concerning the break-up of Gondwana: 'Were the Early Jurassic flood basalts of South America, South Africa, and East Antarctica produced by a hot spot, or do they signal the beginning of break-up?', 'Why did Gondwana break apart, in the first place?', 'Why did the break-up take place in 3 distinct stages {Middle Jurassic, Early Cretaceous. Late Cretaceous)?'.
During the Late Cretaceous. Gondwona was in its final phase of dispersal, yet important questions remain, 'Why can't we get the older M anomalies to fit togther properly?', 'What caused the Deccan flood basalts?', 'Is there a relationship between these flood basalts and the K/T extinction?', 'When was the ligation between Africa and South America terminated?', and 'How did those darn dinosaurs get from Africa to India in the Late Cretaceous?!'. I would like answers to these questions. Realizing, however, that it is often easier to ask questions rather than seek out solutions, I would like to review various solutions and relate my own answers to these questions, however fantastic and controversial they may be.

The present study consists of generation of 3D perspective
view of very high resolution satellite gravity data over the western Indian offshore region and its correlation with known tectonic  features such as the Bombay High, the Chagos – Laccadive ridge complex, the Laxmi ridge and basin etc.