Stratigraphy and Structure of the Precambrian Banded Iron Formation and Chromite-Bearing Ultramafic Rocks of Sukinda Valley, Orissa

The Sukinda Valley of Orissa is underlain by the banded iron formation (BlF) and chromite-bearing ultramafic rocks of Precambrian age. Besides these, local exposure of a quartz-arenite bed with basal conglomerate is correlated with the Kolhans. A basal quartzite horizon is conformably overlain by the BIF. lhe quartz-arenite (Kolhans?) with a conglomerate at the base lies with a local disconformity over the BIF. Chromitebearing ultramafites are pre-kinematic intrusives into the iron formation and have been co-folded with the older sediments. Orthopyroxenite and granitic rocks are intrusive into the chromiferous ultramafites. Occasional intrusive dolerite dykes in the valley may be correlated with the Newer Dolerites of Singhbhum.

The regional structure of the Precambrian rocks of the Sukinda Valley, as established by the present authors, is a cross-folded doubly plunging syncline with the culminated fold axis striking ENE-WSW which is parallel to the main fold axis of the Eastern Ghats Orogenic belt. The plunge of the main fold axis is towards NE and wsw. The cross-folded axis, lying between Tungaisuni and Champajhar villages, trends NNW-SSE and is subparallel to the cross-folded axes of the Eastern Ghat Orogenic belt.