Grain Size Characteristics of Ancient Fluvial Deposits - An Example from Lower Gondwana (Permian) Formations Pench Valley Coalfield, Central India

Abstract

Probability plots of grain size analysis of Lower Gondwana Sandstones reveal three types of grain size distribution characterised by one, two and three inflection points between sediment populations. In the given sandstones, traction load occurs in minor (< 1.0%) to small (~15%) proportion, but may be locally abundant (~71%). Saltation load generally forms the bulk of the sediment, and fine clastics as suspension load occurs in subordinate amount. Probability plots reveal overlapping particle size limits between traction and saltation loads and saltation and suspension loads. Analysis of inclination values of probability plots suggests that traction load is poor - to moderately sorted; saltation population on the average moderately - to well sorted in the case of Talchir and Barakar sandstones, but poor - to moderately sorted for sandstone of the Motur Formation. Relevant attributes of sediment size are genetically interpreted, in order to decipher differencesbetween the processes which operated during the deposition of Lower Gondwana sandstones in the Pench Valley basin.