I read about this in a post on Yahoo News, which has so far attracted more than 9,500 comments in less than three days. A disturbingly large number of responses are convinced the actual culprit was a global flood. I've read enough in science books (and on this site--thanks!) to realize that doesn't 'hold water,' but some people have raised a question I realized I don't have an answer for.

With so many individuals supposedly dying over a short period of time, should we expect to see a denser concentration of fossils in the KT boundary? I've read about the rarity of the fossilization process, and that many environments are not even conducive to it. But with so many more potential fossilizing events, is it surprising that we don't see a concentration of certain species we know went extinct then? I'm thinking they would still be exposed to the elements, scavengers, etc. and broken down before being preserved, but I'm not sure.

Here are the details of the article - it would seem reasonable to assume they know what they are talking about!

The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary
Peter Schulte,1,* Laia Alegret,2 Ignacio Arenillas,2 José A. Arz,2 Penny J. Barton,3 Paul R. Bown,4 Timothy J. Bralower,5 Gail L. Christeson,6 Philippe Claeys,7 Charles S. Cockell,8 Gareth S. Collins,9 Alexander Deutsch,10 Tamara J. Goldin,11 Kazuhisa Goto,12 José M. Grajales-Nishimura,13 Richard A. F. Grieve,14 Sean P. S. Gulick,6 Kirk R. Johnson,15 Wolfgang Kiessling,16 Christian Koeberl,11 David A. Kring,17 Kenneth G. MacLeod,18 Takafumi Matsui,19 Jay Melosh,20 Alessandro Montanari,21 Joanna V. Morgan,9 Clive R. Neal,22 Douglas J. Nichols,15 Richard D. Norris,23 Elisabetta Pierazzo,24 Greg Ravizza,25 Mario Rebolledo-Vieyra,26 Wolf Uwe Reimold,16 Eric Robin,27 Tobias Salge,28 Robert P. Speijer,29 Arthur R. Sweet,30 Jaime Urrutia-Fucugauchi,31 Vivi Vajda,32 Michael T. Whalen,33 Pi S. Willumsen32

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 asteroid impact 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.