ABSTRACT

A detailed lithologic and petrographic study of the sedimentaries of the Giridih Basin was under taken. The chief rock types belonging to the Lower Gondwana subdivision (Upper Carboniferous) are represented by two stages, Talchir and Karharbari.

The Talchir Stage consists of a boulder bed, needle shales, with alternating lenses of silty sandstones, and coarse grits. The boulder bed is unfossiliferous as are the silty sandstones and the coarse grits, but the needle shales frequently contain inclusions of carbonaceous material.

The Karharbari Stage starts with a conglomerate at the base and consists chiefly of alternating grey arkoses, micaceous shales, carbonaceous shales, and coal seams. The arkoses are cross bedded, the cross bedding being of the type that is usually characteristic of shallow water current.

All lines of evidence suggest that the Talchirs are in part glacial and in part glaciofluvial and that the lake basin became shallower at the close of the Talchir period. The Karharbari sediments were interpreted as having been deposited in shallow water and based on cross bedding and heavy mineral constitution were thought to have been derived from a proximate western source.