Fire activity across Cretaceous/Paleogene transition: Evidence from pyrogenic biomarkers preserved in the Mahadeo‐Cherrapunji section, Meghalaya, India

Abstract

Previous studies on high concentrations of polycyclic aromatic hydrocarbon (PAHs) present in the shallow‐marine Um‐Sohryngkew River (USR) Cretaceous/Paleogene Boundary (KPB) section suggested regional fire incidences and biotic stress on life. However, such observations at the USR site have not been confirmed so far anywhere else in the region, we, therefore, do not know whether the signal was local or regional. Thus, to find out charred organic markers associated with the shelf facies KPB outcrop (at a distance of over 5 km) of the Mahadeo‐Cherrapunji road (MCR) section, PAHs were analyzed using gas chromatography–mass spectroscopy. Data show a notable rise in the PAHs and exhibit maximum abundance in the shaly KPB transition layer (in biozone P0) and the immediately underlying layer. The PAH excursions match well with the major incidences of the Deccan volcanic episodes and convergence of the Indian plate with the Eurasian and Burmese plates. These events were responsible for seawater disturbances and eustatic and depositional changes, including the retreat of the Tethys. The incidence of high amount of pyogenic PAHs unrelated to the total organic carbon content is suggestive of wind‐blown or aquatic system transportation. A down‐thrown shallow‐marine facies of the Therriaghat block was responsible for an early accumulation of PAHs. However, the spike of perylene in the immediately underlying KPB transition layer is plausibly linked to the Chicxulub impact crater core. Anomalous concentrations of combustion‐derived PAHs together with the high fragmentation and dissolution of the planktonic foraminifer shells show marine biodiversity and biotic distress. Significantly, the pyrogenic PAH excursions are restricted to either the KPB layer itself or strictly below or above it, indicating regional fire incidences and attendant KPB transition (66.016 ± 0.050 Ma).

Coronene - A Potential Powerful Tool for Reconstructing Ancient Fire Records and Its Significance in a Geological Context

“…The magma activity of the Deccan Traps peaked just a few tens of thousands of years before the mass extinction. Strata from the K-Pg boundary in India, located about ~1000 m from the Deccan Traps, suggest a link between the traps' activity and PAHs including coronene, although only one study has been conducted so far (Pal et al, 2023). In the Mahadeo-Cherrapunji road (MCR) section, the highest concentration of PAHs is found in the shaly transition layer of the K-Pg (Pal et al, 2023).…”

“…Strata from the K-Pg boundary in India, located about ~1000 m from the Deccan Traps, suggest a link between the traps' activity and PAHs including coronene, although only one study has been conducted so far (Pal et al, 2023). In the Mahadeo-Cherrapunji road (MCR) section, the highest concentration of PAHs is found in the shaly transition layer of the K-Pg (Pal et al, 2023). These PAH variations align closely with major events of the time, including the Deccan volcanic activities and the merging of the Indian plate with both the Eurasian and Burmese plates.…”