The Great Vindhyan Basin of Northern India

Abstract The Vindhyan Basin, extending from Sasaram to Agra and Nimach, occupies an area of about 70,000 sq. miles. The Semri Series, constituting the Lower Vindhyans, show mainly argillaceous and calcareous strata with glauconitic beds and volcanics. They were subjected to diastrophism before the Upper Vindhyans, composed mainly of arenaceous and argillaceous strata, were laid down. The shape of the basin indicates that it must originally have extended in to the Lesser Himalayan region of Nepal and Garhwal-Simla. Though the Vindhyan formations have not yielded any fossils useful for a clear determination of their age, they are considered to be mainly Cambrian. The Lesser Himalayan region contains several unfossiliferous formations (Simla Slates, Jaunsars, Blainis, and Infra Krol-Krol-Tal Series) whose stratigraphic correlation has so far hinged on the view that the Blaini boulder beds are of Talchir age. Consequently the Infra-Krol, Krol and Tal Series have been correlated with the Mesozoic systems. Recent work by Boileau and his associates in the Lesser Himalayas has led them to offer a new correlation. Boileau suggests that the Vindhyans represent a good part of the Palaeozoic; that the Blaini tillites are contemporaneous with an ice age at the heginning of the Upper Vindhyan, following the diastrophism which affected the Semri Series; and that a part of the Tals are the equivalents of the Talchirs. In this paper the authors review the stratigraphy of the regions concerned and bring out the implications of the interesting correlations suggested by Boileau.