Santanu Ghosh

The present investigation reports the detailed saturated and aromatic biomarker distributions in seven Early Permian coal samples using the conventional gas chromatography–mass spectrometry (GC–MS) and comprehensive GC × GC–time‐of‐flight (ToF)–MS techniques to reveal new insights into organic matter (OM) source, deposition conditions, and thermal maturity. The coal samples from the Karharbari and Barakar Formations of the Ib‐Valley Basin, Odisha, India, reveal a predominance of intermediate chain‐length n ‐alkanes (51.83%–63.61%) and low odd‐over‐even carbon preference (OEP = 0.31–1.91), likely suggesting OM derivation from aquatic plants and/or terrestrial shrubs/herbs. The identification of saturated bicyclic (C ₁₆ –C ₁₈ ), tricyclic (abietane, norabietane, 4β(H)‐19‐norisopimarane), and tetracyclic diterpanes (16β(H)‐phyllocladane, 16β(H)‐ ent ‐kaurane, 16α(H)‐ ent ‐kaurane, norkaurane), along with isohexyl alkylnaphthalenes, retene, tetrahydroretene, and bisnorsimonellite in the aromatic fraction, suggests a significant contribution from Glossopteris flora and/or primitive conifers. High abundances of C ₂₉ regular steranes and diasteranes further support the contribution from terrestrial swamp vegetation. Redox‐sensitive parameters, including pristane/phytane ratios, Pr/ n ‐C ₁₇ versus Ph/ n ‐C ₁₈ , alkylated dibenzothiophenes, dibenzofurans, and methyltrimethyltridecylchromans (MTTCs), with MTTC index values of 0.32–0.58 and α‐/γ‐MTTC ratios of 0.61–2.10, reflect peat accumulation under fluctuating oxic–anoxic conditions within a marginal marine environment. Thermal maturity assessments based on biomarker parameters, such as C ₃₁ 17β(H),21β(H)‐homohopane, C ₂₉ diasterane/sterane ratios, methylphenanthrene indices, and methyldibenzothiophene isomer ratios, suggest that the coals have attained peak catagenetic maturity, with estimated equivalent vitrinite reflectance values ranging from 0.57% to 0.68%. These molecular‐level insights provide a comprehensive understanding of the origin, depositional environment, and maturation history of Early Permian coals from the Ib‐Valley Basin.

Objectives: To evaluate heavy mineral assemblages as reliable indicators of sediment provenance and mineralogical maturity in the Barail Group sandstones exposed between Khawzawl and Champhai, Mizoram. Methods: Heavy mineral analysis was performed to determine provenance and maturity using standard petrographic and mineral separation techniques. Twenty-eight representative sample portions were gently crushed and soaked to remove clay coatings, followed by chemical treatments to eliminate carbonate, iron oxides, and organic matter. After drying and sieving (80‑mesh fraction), heavy minerals were separated using bromoform and mounted on glass slides with Canada balsam. Mineral identification and counting were carried out under a polarizing microscope, and the ZTR index was calculated to quantify sediment maturity. Findings: The heavy mineral suite includes zircon, tourmaline, rutile, sillimanite, kyanite, staurolite, garnet, epidote, hornblende, and opaque minerals, indicating mixed metamorphic, igneous, and recycled sedimentary sources from an orogenic hinterland. ZTR values range from 43.24 to 71.25, signifying mineralogically immature to submature sandstones. These results suggest moderate degrees of weathering, sediment recycling, and hydraulic sorting during transport and deposition. Novelty: This study provides the first detailed heavy‑mineral‑based assessment of Barail sandstones in Mizoram, establishing new insights into Oligocene sediment routing, provenance, and depositional maturity within the Indo‑Myanmar foreland region. Keywords: Heavy minerals, provenance, Barail Group, ZTR Index, Mizoram