The Petrographic Correlation of Bachra Seams, Bachra Area, North Karanpura Coalfield, Bihar, India

In the south-eastern portion of the North Karanpura coalfield, Bihar, two coal seams, known as Upper Bachra and Lower Bachra in the Bachra area, and Ray Top and Ray Bottom in the contiguous Ray area, occur in the Karharbari formations. The geology of these areas is indicative of the Bachra seams being the eastern extension of the Ray seams. Their correlation by coal petrography has been attempted in the present paper.

To evaluate the applicability of petrographic method in seam correlation, composition by group maceral and microlithotype was determined for fourteen coals from eight Gondwana coalfields; the microlithotype composition was more characteristic of the petrographic nature of coals. Petrographic profiles of Bachra seams were prepared; they depict the petrographic naturem which varies from seam to seam. The microlithotype composition of Churi, Ray Top, Argada, and Sirka seams was determined on seam total basis; it indicated that each of the seams has a distinctive composition being different for different seams.

The petrographic composition by group maceral, microlithotype, and "group microlithotype" of the Bachra and Ray area seams was determined on scam total basis and correlations made. The composition of Upper and Lower Bachra was found to be similar to that of Ray Top and Bottom seams respectively; the former are, therefore, the eastward extensions of the latter.

The present paper introduces the applicability of coal petrography in correlation of Indian coal seams. It also presents the first petrographic profile of any Indian coal seam.