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The results of the petrological investigations carried out on coal samples from the Oligocene deposits of Northeastern India (Assam, Arunachal Pradesh and Nagaland) have been discussed. These deposits occur in the Tikak Parbat Formation (Barail Group) and were probably deposited in the foreland basin. Petrographically, these coals are enriched in vitrinite macerals (65.8-96.6 vol %, mean 87.2 vol %) with variable concentrations of liptinite macerals (2.7-35.4 vol %, mean 11.9 vol %). They contain low concentration of inertinite (nil-3.3 vol %, mean 0.9 vol %) macerals. The microlithotype is dominated by vitrite (61.5-100 vol %, mean 90.8 vol %). An elevated volatile matter (44.15 -60.20 wt %, mean 52.90 wt %, d.a.f. basis) and reflectance values (VRr 0.39-0.61%) put their rank as sub-bituminous type 'C' to high volatile bituminous type 'C'. The GI and TPI values favour telmatic conditions of origin with high tree density and prolonged wet conditions. This is in agreement with the paleoenvironment interpreted from the vitrinite and liptinite-rich microlithotypes, which suggested a forest and reed facies. However, the presence of inertinite in some coal seams indicates tectonic upheavals / regression of the sea resulting to periodic and short span dryness of the basin.

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The present paper entails the petrographic and chemical characteristics of the lignite samples drawn from the Rajpardi lignite deposit of Bharuch district, Gujarat. This lignite contains a high concentration of huminite which is dominated by telohuminite, followed by detrohuminite. Liptinite and inertinite macerals are very low in concentration. The dominant microlithotype is humite. Its elevated volatile matter and high hydrogen content depicts its perhydrous nature. The study reveals that this lignite originated in a limno-telmatic to telmatic condition. The paleomire is further characterized as a wet moor having moderate to high flooding with good tissue preservation and increasing bacterial activity.