Assam Arakan Basin

The Upper Assam and Purvanchal Range of the North-eastern India and its adjoining Shilong Plateau and Mikir Hills exposes a vast thickness of Cenozoic formations. The cenozoic formations were deposited over the basement of Precambrian rocks and Lower Gondwana Group. The oldest fossiliferous sequence of the region contains fossil assemblages indicating Upper Cretaceous age, which marks the marine transgression over the region. (Late Campanian—Maestrichtian). There is an Ophiolite sequence coinside with the phase of regional metamorphism that took place before the deposition of Upper Eocene.