Grain size analysis of the Renji Formation (Barail) and Bhuban Formation (Surma) sandstones in the Barak basin, Manipur, India: Implication for nature of transport and depositional environment

The grain-size analysis in the sandstones of the Renji Formation (Barail Group) and Bhuban Formation (Surma Group) in parts of the Barak Basin, western Manipur, India was carried to determine the grain size distributions, modes of sediment transportation and depositional environment. The grain size of the Barail sandstone ranges from 2.3ɸ to 3ɸ and their grains show well sorted to moderately well sorted, symmetrical to coarse - skewed as well as nearly very fine – skewed and mesokurtic nature whereas the grain size of the Surma sandstone varies from 2.7ɸ to 3.4ɸand these grainsdisplay moderately well sorted to moderately sorted, coarse - and symmetrical skewed, mesokurtic to very leptokurtic nature. The Kurtosis analysis shows that the Barail siliciclastic sediments have been sorted in normal energy condition, whereas the Surma siliciclastic sediments likely have been sorted in normal to low as well as high energy conditions. Generally, the Barail and Surma sandstones show unimodal distribution. A shallow marine environment has been envisaged for the deposition of sediments of both the Barail and the Surma sandstone, dominated by saltation process.