Organic geochemistry and petrology of the coals in the Laisong Formation, Naga Schuppen Belt, NE India: Inferences on hydrocarbon potential and depositional environment

Abstract

The Oligocene Laisong Formation in the Naga Schuppen Belt is coal bearing along the Dimapur-Kohima Road section, Nagaland. The coals are sulphurous and classified as lignite to sub-bituminous 'C' based on various rank parameters. The coals are dominantly composed of vitrinite followed by inertinite and liptinite in order of abundance. The coals have high-quality Type III kerogens derived mainly from angiosperm plants. The richness and quality of organic matter in the coal is excellent to act as a petroleum source rock. Most of the maturity parameters indicate that maturity ranges from immature to early mature. The biomarker parameters and facies critical maceral associations point to deposition of the coal-bearing strata in non-marine/ terrestrial depositional environment under moist hydrodynamic conditions, possibly in an upper delta plain environment. However, the high sulphur content of the coal points to deposition in a lower delta plain environment. Comparison with other Palaeogene coal deposits of the same sedimentary basin shows that the Laisong coals contain lesser amount of liptinite macerals and much higher amount of sulphur than these deposits. All these deposits are of similar rank, however, the Laisong coals show marginally low thermal maturity from the viewpoint of hydrocarbon generation.

Rock-Eval Pyrolysis and Petrographic Characteristics of Coals of Chintalapudi Sub-Basin, Pranhita-Godavari Basin, Southern India: Implication to Depositional Environment

“…Organic petrography deals with the microscopically visible organic matter present in rocks and is the most effective method for determining the depositional environment, the source vegetation,and the maturation level of coal and its gas generation potential (Diessel, 1983;Flores, 2002;Kalkreuth , 1991;Latif , 2021). Many researchers have provided a thorough study of several geochemical parameters in evaluating the richness, maturity and quality of source rocks, vitrinite reflectance, maceral analysis, total organic content measurement, rock-eval pyrolysis, associations between maturity and hydrocarbon generation, as well as the depositional environment (Dow, 1977;Tissot and Welte, 1978;Thompson-Rizer, 1993;Law, 1999;Vandenbroucke and Largeau, 2007;Gogoi , 2008;Salleh , 2008;Sahoo and Gogoi, 2011;Phukan , 2013;Jahan, 2016;Sharma , 2016;Singh , 2016aSingh , -b, 2017aMathews , 2020;Gogoi , 2020Gogoi , , 2021Singh and Kumar, 2020;Singh , 2022;Kar , 2022). Quantitative and qualitative analyses of different kerogen types with the geochemical study of organic matter provide a better understanding of the generating potential (GP) of source rocks (Thompson and Dimbicki, 1986;Isabel, 2012).…”

Introduction, Part 2—Geodynamic evolution of Eastern Himalaya and Indo‐Myanmar orogenic belts: Advances through interdisciplinary studies

“…This Special Issue‐ Part 2 is a continuation of earlier Special Issue‐ Part 1 published in vol. 57 (2), of Geological Journal , which contained 26 research articles (Ao & Satyanarayanan, 2022; Baral et al, 2022; Bhowmik et al, 2022; Bora, Borah, et al, 2022; Bora, Mukherjee, et al, 2022; Deb & Ray, 2022; Devi & Singh, 2022; Devrani et al, 2022; Doley et al, 2022; Gogoi et al, 2022; Gupta et al, 2022; Hazarika & Kayal, 2021; Imtisunep et al, 2022; Liu et al, 2022; Luirei et al, 2022; Lukram & Tandon, 2022; Bidyananda et al, 2022; Majumdar, Gogoi, & Ghatak, 2022; Majumdar, Gogoi, Ghatak, Saikia, et al, 2022; Mukherjee et al, 2022; Pebam et al, 2021; Rashid et al, 2022; Saikia et al, 2022; Singh and Kshetrimayum, 2021; Singh, Guruaribam, Singh et al, 2022; Singh, Singh, Singh, et al, 2022; Srivastava, 2021; Srivastava & Kichu, 2021). Figure 2 displays the area of study of 29 papers included in this Special Issue 2.…”