TIDAL RHYTHMITES WITHIN EARLY PERMIAN BARAKAR FORMATION, KHUDIA NALA, RANIGANJ BASIN, INDIA

Abstract

The early Permian Barakar Formation was known to have been deposited in a fluvial depositional setting. But evidences of primary sedimentary structures that are exclusively tidal in origin are interpreted through detailed sedimentological analysis of the Barakar Formation along Khudia Nala section. Raniganj Basin. The tidal signatures include alternate sandstone and mudstone dominated intervals of variable thickness indicating energy fluctuations, sandstone foreset draping by mud indicating slackwater phases, double mud drape structures indicating two successive slackwater phases, laterally and vertically accreted cross-strata sets where lateral accretion is understood by presence of reactivation surfaces and vertical accretion is identified by intermittent thin sandstone-mudstone plane laminations. Apart from these, there are inclined heterolithic strata in which we got flaser and lenticular bedding that are typical of tidal environment and bi-directional cross-strata sets which gave rise to herring-bone crossstratification locally. Measurements of the alternate thicker and thinner larnina set manifests spring-neap tidal fluctuation and provides clue to understand the moon-earth orbital forcings.