Megascopic Carbonaceous Remains from Proterozoic Basins of India

Megascopic carbonaceous remains, occurring on the bedding planes of the areno-argillaceous successions of the Precambrian, are the important evidence of the early life forms. A wide variety of such forms are described from the Proterozoic successions of India viz., the Vindhyan, Chhattisgarh, Kurnool and Bhima basins in peninsular India and some of the carbonate belts of the Lesser Himalaya. The Chuaria–Tawuia assemblage invariably constitutes the most important element of megascopic carbonaceous remains in these basins. Besides, simple films to morphologically complex forms are also recorded. In the present paper, knowledge and status of megascopic carbonaceous remains entombed in these successions of India with their significance in understanding the earth’s earliest biosphere are reviewed. Two principal questions are addressed: Are these carbonaceous mega-remains divulge any evolutionary steps and event in the Precambrian? Is there any discernable biostratigraphic potential in these carbonaceous mega-remains in space and time? The review reveals that coccoidal/spherical propkaryotic forms attained gigantism for the first time around Palaeoproterozoic/Mesoproterozoic boundary and this phenomenon was repeated in the geiological history around cryogenian. Eukaryotic carbonaceous remains show morphological changes from simple non processed to processed forms. A scheme of biozonation on the distribution pattern of the carbonaceous mega-remains in the Proterozoic successions, with form and function of the some of these remains, is presented.