A large international, multidisciplinary, team of scientists use stratigraphy, chemistry and sedimentary analysis to prove an extinction causing impact at the turning point of two geological and biological ages. Younger Dryas Boundary Team, PNAS, 2007? Nope. KT Team iteration 2010, today in Science.
A team of thirty or so drove another long nail in the coffin of volcanoes as the cause of the KT-Boundary extinction. The lately smoldering debate, which is analogous and precedes the now raging Younger Dryas Boundary debate, seems to be drawing to a close. Today’s paper is a good sum-up of the precision with which the KT catastrophe has been documented with physical evidence. The contrary conclusions of Gerta Keller have been seriously undermined.
My hope, of course, is that the years of deserved research and intense attention to the dinosaur-extinction-by-space-rock debate, can be marshaled once more on behalf of the Ice-Age-animals-wiped-out-by-disintegrating-comet theory. A guy can hope, right!?
The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroidimpact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.