The recent discovery of the direct link between Deccan volcanism and the end-Cretaceous mass extinction also links volcanism to the late Maastrichtian rapid global warming, high environmental stress, and the delayed recovery in the early Danian. In comparison, three decades of research on the Chicxulub impact have failed to account for long-term climatic and environmental changes or prove a coincidence with the mass extinction. A review of Deccan volcanism and the best age estimate for the Chicxulub impact provides a new perspective on the causes for the end-Cretaceous mass extinction and supports an integrated Deccan-Chicxulub scenario. This scenario takes into consideration climate warming and cooling, sea-level changes, erosion, weathering, ocean acidification, high-stress environments with opportunistic species blooms, the mass extinction, and delayed postextinction recovery. The crisis began in C29r (upper CF2 to lower CF1) with rapid global warming of 4 °C in the oceans and 8 °C on land, commonly attributed to Deccan phase 2 eruptions. The Chicxulub impact occurred during this warm event (about 100–150 k.y. before the mass extinction) based on the stratigraphically oldest impact spherule layer in NE Mexico, Texas, and Yucatan crater core Yaxcopoil-1. It likely exacerbated climate warming and may have intensified Deccan eruptions. The reworked spherule layers at the base of the sandstone complex in NE Mexico and Texas were deposited in the upper half of CF1, ~50–80 k.y. before the Cretaceous-Tertiary (K-T) boundary. This sandstone complex, commonly interpreted as impact tsunami deposits of K-T boundary age, was deposited during climate cooling, low sea level, and intensified currents, leading to erosion of nearshore areas (including Chicxulub impact spherules), transport, and redeposition via submarine channels into deeper waters. Renewed climate warming during the last ~50 k.y. of the Maastrichtian correlates with at least four rapid, massive volcanic eruptions known as the longest lava flows on Earth that ended with the mass extinction, probably due to runaway effects. The kill mechanism was likely ocean acidification resulting in the carbonate crisis commonly considered to be the primary cause for four of the five Phanerozoic mass extinctions.

Palynological studies of the late Maastrichtian infratrappean and intertrappean sedimentary beds from various stratigraphic levels in the Deccan continental flood basalt of the Nand-Dongargaon Basin in central India show that infratrappean sediments (Maastrichtian C30n-C29r) are characterized by gymnosperm ( Araucariacites , Classopollis , Cycadopites , Podocarpidites ) and angiosperm ( Cretacaeiporites , Compositoipollenites , Graminidites , Longapertites , Palmaepollenites ) palynomorphs. A distinct floral turnover is observed in intertrappean sediments with the initiation of volcanic activity in the basin. At the lowest stratigraphic level, the earliest floral change is recorded by the appearance of angiosperm-pteridophyte–dominated association ( Aquilapollenites , Azolla , Gabonisporis , Tricolpites , Triporopollenites , and Normapolles group pollen) and the appearance of peridinoid dinoflagellates. At higher stratigraphic levels in C29r, this palynofloral association continues with the appearance of new forms, such as Scabrastephanocolpites spp., Scollardia conferta , and Triporopollenites cracentis . A sharp decline in diversity of titanosauriform-abelisaurid–dominated dinosaurian fauna is also observed with the onset of Deccan volcanic activity. At this time, out of at least eight dinosaur species, only a single taxon of titanosauriform dinosaurs survived the onset of volcanism. This suggests that the floral change and decreased dinosaur diversity are strongly linked with the initiation of Deccan volcanism in C29r in India. The peak eruption of this volcanic phase resulted in the Deccan's largest volume of lava flows, which played a significant role in the global mass extinction at the Cretaceous-Paleogene boundary.

During the last two decades, extensive paleontological research in the main Deccan volcanic province has led to a better understanding of biodiversity close to the Cretaceous-Paleogene boundary. Several infratrappean localities exposed in Jabalpur, Kheda, Balasinor, Rahioli, Dohad, and Bagh in the Narmada Valley (India) preserve one of the most geographically widespread dinosaur nesting sites known in the world. The well-studied intertrappean beds, such as those of Naskal on the southern margin, Asifabad and Nagpur on the eastern margin, Kisalpuri and Mohgaon Kalan on the northeastern margin, and Anjar on the northwestern margin of the main Deccan volcanic province, have yielded Maastrichtian fish ( Igdabatis ) and dinosaur remains and palynofossils ( Aquilapollenites - Gabonisporites - Ariadnaesporites ), either separately or in association, that suggest a Maastrichtian age for these beds. Only two intertrappean sections, Papro on the northern margin and Jhilmili on the northeastern margin of the main Deccan volcanic province, have produced Paleocene fossils. The fossil record from the infratrappean and intertrappean beds demonstrates that the dinosaurs survived the early phase of volcanism, though there was an apparent decline in their diversity, and that freshwater vertebrate fauna was least affected by the initial volcanic activity. The episodic nature of Deccan volcanism may possibly explain the survival of many freshwater and terrestrial communities during the periods of quiescence. In addition, as in the case of the late Maastrichtian sections in eastern Montana, North America, detritus-feeding freshwater vertebrate communities possibly had greater potential for survival than the terrestrial communities dependent on primary productivity. A close examination of the vertebrate faunal distribution across the two stratigraphic intervals (infratrappean and intertrappean) suggests that sampling bias in the infratrappean beds may have also masked the actual diversity of these beds.

Abstract: Palynological studies of Deccan volcanic associated sediments of the Sahyadri Group of Nand-Dongargaon basin of Maharashtra, Amarkantak Group of Chhindwara and unclassified Deccan Trap sequences of Saurashtra show the presence of Aquilapollenites pollen. The overall data on this genus from the Indian Late Cretaceous-Early Paleocene indicates that the genus was widely distributed during the Late Cretaceous. A notable decline in abundance in the Early Paleocene may be related to the climatic and environmental changes brought about by the Deccan volcanism.