How the Deccan Volcanism and the Chicxulub Asteroid Impact Resulted in the Biological Crisis Ending the Mesozoic Era

The direct causes for the end-Cretaceous biological crisis are still enigmatic despite of the numerous studies carried out at the Chicxulub asteroid impact site and in the Indian late Cretaceous Deccan volcanic province. None of the discussed physical and chemical devastating factors explained the selective extinction-survival pattern. The present study analyzes the vulnerability of faunal and floral groups to a sudden ecological disaster as the result of the incidental co-occurrence of the asteroid impact during Deccan volcanism. Their combined ejecta must have shaded the sunlight, ceasing photosynthesis for about 2-3 years and lowering the temperature on earth, which must have been crucial for cold-blooded reptiles. The darkening would have blurred seasonality, drastically reducing floral blooming, fruition and organism reproduction, all of which resulted in the collapse of the marine and terrestrial food-chain and prey-predator relationships. Apart from death by starvation, the main killing was carried out by the organisms themselves through a Darwinian struggle for life leading to a selective elimination of the temporarily vulnerable taxa. Those which succeeded to escape adapted to refuge sites and survived. The disappearance of most of the Cretaceous carnivore reptiles enabled the survivors to fearlessly explore the Tertiary world and acclimatize to previously inaccessible habitats, which continuously shaped with the ongoing changes in the ecological and biological settings. This dynamic development of the Tertiary ecosystems accelerated the evolutionary tempos leading to rapid speciation. Despite being direct descendants of Cretaceous survivors they were given a new taxonomic identity and their precursors were considered wiped-out, intensifying the apparent end-Cretaceous ‘mass extinction’.