A roughly 10.5‐m‐thick succession within the Langpar Formation of the Um Sohryngkew River section, Meghalaya, India, constrained by the last occurrence of Globotruncanita stuarti and the first occurrence of Parasubbotina pseudobulloides, spans the K/T (Cretaceous–Tertiary) transition. The unit is divisible into three parts with the lower consisting of shaly limestone, weakly calcareous shale and silty shale with coal streaks. The middle part is dominated by calcareous shale with mud flakes, coprolites, burrows and pyrite nodules, followed by alternating limestone and marlite at the top. Planktonic foraminifera are rare to frequent within the unit. Based on the distribution of zonal indices, seven successive planktonic foraminiferal zones are recognized from across the K/T boundary. From base to top, these are CF4, CF3, CF2 and CF1 in the upper Maastrichtian part and Zone P0, Zone Pα and Subzone P1a in the lower Danian part. The biozones indicate that the section is biostratigraphically continuous across the K/T boundary. A similar foraminiferal succession and K/T transition is observed in the Langpar of the Cherrapunji‐Mahadeo road section at a distance of over 5km. These K/T outcrops from Meghalaya provide the first record of a continuous K/T sequence in the Indian subcontinent with respect to planktonic foraminifera.
A combustion-derived polycyclic aromatic hydrocarbon (PAH) compounds based high-resolution stratigraphic records across the Cretaceous/Palaeogene boundary section of the Um Sohryngkew river section is presented in this paper. The yellowish brown, organic-rich, 1 to 2 mm thick, clay layer in biozone CF3 is marked by sudden increase in the high molecular weight fluoranthene, pyrene, chrysene, benzo(a) anthracene PAH compounds. These componds are similar to those associated with the well-known K/Pg boundary sections across the world. Besides these, high abundance of low molecular weight 3 ring anthracene and fluorine, and 4 ring PAH compounds is also noticed in this layer. Subordinate amount of low molecular weight 3-ring phenanthrene, 3-methylphenanthrene, 2-methylphenanthrene, 9-methylphenanthrene and 1-methylphenanthrene PAH compounds have also been found in the successive layer of biozone CF2. Occurrence of high molecular weight PAH compounds in the biozone CF3 (66.83-65.45 Ma age) imply global fire, induced by the heat supplied by Abor/ Deccan volcanic activity, possibly linked with the K/Pg boundary transition events as later initiated prior to the K/Pg boundary, however, the main episode of Deccan volcanic activity occurred ~300 ky earlier or at the K/Pg boundary itself. PAH compound anomalies in the biozone CF3 is well coinciding with the well documented Ce anomaly layer, but, preceded by planktonic foraminiferal break and PGE anomaly bearing layer in the biozone P0. It is inferred that the K/Pg boundary related global fire played significant role in the collapse of the ecosystem, causing sudden demise of organisms.
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