A Reappraisal of the Depositional Environment of the Precambrian Metasediments around Ghatsila-Galudih, Eastern Singbhum

Early Proterozoic Chaibasa Formation around Ghatsila-Galudih region comprises a number of cyclic fining-upward prograding sequences of tidalites. Each cycle begins with a basal flat-bedded to cross-bedded quartzit.e that passes into phyllite/ schist through a zone of alternating quartzite-phyllite/schist. Occurrences of large-scale cross-bedding, reactivation surface, mud cracks, fiaser, lenticular bedding and wave ripples coupled with channels and scours and evidence of strong current variability suggest deposition by tractional current in tidal fiats rather than in deep-sea environment by turbidity current. Dominance of unidirectional current structures results· from migration of bedforms only during the dominant phase of the tidal current.