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Datta, A. K.
- Tectonic Framework and Subsurface Stratigraphy of the Ganga Basin
Authors
1 Institute of Petroleum Exploration, Oil & Natural Gas Commission, Dehra Dun, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 12, No 3 (1971), Pagination: 222-233Abstract
Significant data on the structure, tectonics and stratigraphy of Ganga basin have been obtained from aeromagnetic, ground magnetic, gravity and seismic surveys and the deep drilling conducted in the basin during the last fifteen years, Based on these data, the Ganga basin has been defined as a major platform depression and classified into seven tectonic zones, viz., Monghyr-Saharsa ridge, East Uttar Pradesh shelf, Gandak depression, Faizabad ridge, West Uttar Pradesh shelf, Sarda depression and Delhi-Hardwar ridge. This classification is based on the continuation of major tectonic trends from the Peninsular shield into the Ganga basin, the variations in the total thickness of the sedimentary cover, and the basement configuration as deduced from different surveys.
The sedimentary cover over most part of the Ganga basin is essentially composed of two main stratigraphic cum structural sequences representing the two main sedimentary stages in the geological evolution of the basin. The oldest, probably corresponding to the Vindhyans, is represented by stable to unstable shelf sediments composed of quartz-arenite-limestone-shale alternations. The younger sequence, unconformably overlying the Vindhyans, corresponds to the Neogene terrigenous clastics (Siwaliks). The structural and stratigraphic data of these sediments have been discussed. The presence of a profound unconformity between these two groups of sediments representing a considerable time gap ranging from (?) late Palaeozoic to Paleogene is an important factor in deciphering the tectonic evolution of the Himalaya. However, towards the northernmost depressed parts of the Ganga Basin, the age of the additional thickness of sediments intervening between the two above mentioned groups remains uncertain.
- Contrasting Volcanic Suites in Naga Hills and Their Bearing on the Tectonic Evolution of the Naga Hills Ophiolite Belt, N.E. India
Authors
1 Geological Survey of India, 2 Church Street, Bangalore 560001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 30, No 1 (1987), Pagination: 33-47Abstract
The 200 km long Naga Hills opiliolite belt which forms the northern part of the Indo-Burman ophiolites is made up of two contrasting volcanic suites. viz.; (1) high-Mg basalts (Mg-number 52 to 71) comparable to mid-oceanic ridge basalts and (2) low-Mg (Mg-number 23 to 49) akin to seamount type volcanism.Based on geological and geochemica 1 evidences, a three stage model comprising (1) marginal basin spreading event, (2) seamount event and (3) collision event, is presented to explain the origin and evolution of the Naga Hills ophiolites.