Biopetrological study of coals from Ramagundam coalfield, Godavari basin, Andhra Pradesh, India

Abstract

A detailed petrographic study of eight coal seams from Ramagundam Coalfield, Andhra Pradesh is presented here. The top section of the coal seam I A, I, II, III A, III and IV contains workable thickness. Reflectance study has revealed that the seams IA (middle), III B, III A, III (top) and IV contain coal of high volatile bituminous C rank. Coal seams I A (top and bottom parts), I, II and III (middle) seams/part thereof are constituted by alternate coal bands of high volatile bituminous C and high volatile bituminous B rank. Besides, coal seam III and coal bands present below I seam have attained intermediate stage (high volatile bituminous C to sub-bituminous A) and high volatile bituminous C rank. Index seam is represented by coal of high volatile bituminous C and intermediate stage of the rank. The maceral study has revealed that the different seams are characterized mostly by the dominance of collinite maceral. Occasionally cracks in the vitrinite bands are filled either by clay or pyrite (grains/framboids) inerals. Exinite is represented by the microspore and megaspores of variable shape and size, sporangia, seeds, resin bodies, tenui and crassi-cutinites and algal elements. Inertinite Group is characterized by fusinite, semifusinite, inertodetrinite, sclerotinite and pyro-and degrade-fusinite macerals. Transition from vitrinite to semifusinite and semifusinite to fusinite is frequently observed. The microlithtype analysis has shown that the shaly coal, bright and dull coal have characteristic composition. These coals have been grouped under three categories as vitric, fusic and mixed (vitro-fusic and fuso-vitric) type. It is inferred that the sight of deposition has been a tectonically controlled slowly sinking basin.