Petrography, Mineralogy and Element Distribution in the Charmuria Limestone, Chhattisgarh Basin, M.P.

The Channuria limestone is characterized by grey-black colour, bedding structure, fine grain size and authigenic pyrite cubes. Petrographically a minimicrite, the rock exhibits a texture composed of dark crinkled and light coloured laminae of lime mud. Pyrite has discordant relationship with laminae, whereas silt-sized terrigenous particles are present in the interlaminar areas. Mineralogically the limestone is made up of low Mg-calcite and quartz. Trace element distribution tndicates that the original mineralogy at the time of deposition was calcitic in nature and its distribution in the rock was controlled by the depositional/diagenetic conditions as well as the detrital clastics supplied into the basin. The depositional environment of the limestone is interpreted as shallow marine lagoonal condition and the site of deposition was very near to shore. The dysaerobic to anaerobic condition which is attributable to the restricted circulation of water and the concomitant slow sedimentation rate were responsible for the development of authigenic pyrite and grey-black colour of the limestone.