On the Stratigraphy and Tectonic History of the Iron Ore Bearing and Associated Rocks of Singhbhum and Adjoining Areas of Bihar and Orissa

The iron ore bearing rocks of Singhbhum and the adjoining areas of Bihar and Orissa consist of two groups with distinct lithological characters. One of these occurs within the Noamundi basin in the western part of the Singhbhum granitic platform, while the other occurs in the Gorumahisani-Badampahar ranges in the eastern part of the platform. Detailed studies indicate that the iron ore bearing rocks of the Noamundi basin (Noamundi group) rest with a slight break on the Jagannathpur lava which is considered equivalent to the Dhanjori lava. Hence the Noamundi group is assigned a stratigraphic position above the Dhanjori group. The iron ore bearing rocks of the Gorumahisani-Badampahar region (Gorumahisani group) underlie the Dhanjori group and hence are assigned a stratigraphic position below these rocks. Each of these rock groups has been affected by independent cycles of deformation, metamorphism and igneous activity as a consequence of which these rocks have been welded into the fabric of the Singhbhum granitic platform. The successive orogenic cycles have been provisionally dated on the basis of geochronological data provided by Sarkar et al, and a revised stratigraphic succession for the rocks of the region has been suggested.