Textural characteristics, mode of transportation and depositional environment of the Bhuban sandstones of Surma Basin (Aizawl, Mizoram): Evidence from granulometric analysis

Grain size analysis is an essential technique in sedimentology that is used to decipher the hydrodynamic conditions, transport mechanism and sediment deposition of detrital sediments. In the present research, a comprehensive grain-size analysis was conducted on the sandstone samples obtained from the Bhuban Formation of Surma Group, which is exposed in and around Aizawl, Mizoram. In this study, grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were utilized to understand depositional processes, depositional mechanisms, and hydrodynamic energy conditions. Furthermore, these techniques helped to distinguish between various depositional environments. Based on the grain-size parameters, it has been observed that most of the Bhuban sandstones are categorized as fine to very fine grained, poorly to moderately sorted, where most of the samples had a coarse skewness, followed by near symmetrical, fine skewness, strongly fine skewness and strongly coarse-skewed and mostly platykurtic conditions. Study suggests that during the deposition of sediments the studied sandstones, are associated with high-energy condition with some riverine input. The bivariate plots suggest that the depositional environment of the studied samples was primarily impacted by rivers, and beaches. The Linear discriminant function (LDF) plots also show that the sediments were deposited in shallow marine condition with the influence of turbidity current and fluvial environment. The Bhuban Group of rocks are mostly deposited by suspension with some rolled sediments, suggesting the supply of generally finer and medium fractions of sediments, as represented by the Passega C-M plots.