Archaean Palaeogeography of Eastern and Northern Singhbhum, Eastern India

Abstract

Geological studies in eastern Singhbhum and critical analysis of Dunn's published work in surrounding regions suggest that during the Archaean times a volcanic geanticlinal arc, now represented by the Dalma lavas, tuffs and agglomerates extended roughly east–west for more than 150 miles. The geosynclinal trough in the southern, concave side of the arc was filled with argillaceous sediments, thin subgraywackes and orthoquartzites derived from a land mass to the south. The trough in the northern, convex side of the arc was filled with a huge thickness of argillaceous sediments associated with graywackes, siliceous limestones, sandstones and pre-orogenic ultra-basic and basic intrusives. Both the troughs near their border with the volcanic arc were filled with pyroclastic materials.During orogenic movements two anticlinoria were formed in the supracrustal sediments above the two troughs separated by a syncline above the geanticline, with a granulite-migmatite core in the heart of the outer geosyncline.