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Saha, S. S.
- Tertiary Sedimentation in the Andaman-Nicobar Geosyncline
Authors
1 Geological Survey of India, Calcutta, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 9, No 1 (1968), Pagination: 32-39Abstract
Andaman orthogeosyncline is continuous with Assam-Burma in the north and Indonesian geosyncline in the south. Andaman-Nicobar group of islands constituting the non-volcanic outer arc of the East Indian Orogen, has a more or less continuous history of Sedimentation throughout the Tertiary era commencing from sometime in the Upper Cretaceous right on to the Recent. The sedimentation gradually changed character with the tectonic development of the geosyncline through geologic time.
Euxinic sediments consisting of black pyritous shales with minor amount or dark impure limestone and gritty sandstones represent the earliest episode of geosynclinal sedimentation in the restricted basins formed by submarine ridges and valleys due to emplacement of ophiolites.
These ophiolites were subaerially denuded to some extent; and during Palaeocene-Lower Eocene, algal limestone and conglomerate and subsequently more finer fractions such as tuffaceous basic wacks and serpentinous and chloritic clay beds followed. Subsidence of the geosyncline which commenced with sedimentation of the Euxinic beds produced a uniform configuration of the geosyncline during Middle Eocene (Kirthar). Andaman flysch consisting of altetnatcly bedded graywackes, siltstone and grey illitic clay beds were deposited throughout the length and breadth in this regular geosynclinal basin till Upper Oligocene when a major orogenic movement overcame sedimentation.
Shallower basins formed within and in the outer margins of the rising emhryonic island arc were filled up during Lower Miocene with foraminifcrallimcstone and shale, and radiolarian and foraminiferal chalk beds.
Middle Miocene witnessed another major orogenic movement which brought out the present configuration of the island arc. Fossiliferous clays and limestones were deposited in peripheral basins during the Pliocene-Pleistocene which are partly raised during quite recent times.
- Geology of Great Nicobar Island
Authors
1 Geological Survey of India, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 16, No 2 (1975), Pagination: 135-142Abstract
The Joint Scientific Expedition to the Great Nicobar Island provided opportunity for obtaining a comprehensive knowledge of the major geological features of the island. The various rock formations were examined and their stratigraphic sequence was established. Major structural features were noted and the geological history of the island is reviewed. This reveals a close similarity with the geology of Andaman Islands. Other aspects studied are economic geology, nature of soils and water resources.- Implication of the Mobile Belt of the Indies Archipelago on the Concept of Continental Drift Between India and Australia
Authors
1 Geological Survey of India, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 17, No 3 (1976), Pagination: 309-321Abstract
The Indies mobile belt stretching from northern Burma through the Indonesian to the Australasian archipelagoes is essentially Upper Mesozoic-Cainozoic in age. It is intercontinental in a sense that it is situated between the continents of India and Australia on one side and Sino-Sunda continent on the other, but essentially intracontinental because subsurface continuity of the continental mass and pre-geosynclinal sedimentary formations can be envisaged between the two sectors of continental mass below the geosyncline.
Studies of the geology of the various parts of the Indonesian mobile belt especially the transverse vertical gelogical cross sections of various segments of the belt in Assam-Burma, Andaman-Nicobar, Mentawal-Sumatra and Australasian sectors, suggest spatial continuity of the continental crust and pre-geosynclinal geological formations below the Upper-Mesozoic-Cainozoic geosynclinal formations of the mobile belt.
Absence of any imprint on the Indonesian mobile belt expected due to continental drift between India and Australia corroborates the view of the non-existence of such continental drift.