Cretaceous–Paleogene extinction event  From Wikipedia, the free
encyclopedia Jump to: navigation, search Artist's rendering of a
bolide impact A Wyoming (U.S.) rock with an intermediate
claystone layer that contains 1000 times more iridium than the
upper and lower layers. Picture taken at the San Diego Natural
History Museum Complex Cretaceous–Paleogene clay layer (gray) in
the Geulhemmergroeve tunnels near Geulhem, The Netherlands.
Finger is on the actual Cretaceous-Paleogene boundary.  The
Cretaceous–Paleogene (K–Pg) extinction event,[a] formerly known
as the Cretaceous–Tertiary (K–T) extinction,[b] was a mass
extinction of some three-quarters of plant and animal species on
Earth—including all non-avian dinosaurs—that occurred over a
geologically short period of time 66 million years (Ma)
ago.[2][3] It marked the end of the Cretaceous period and with
it, the entire Mesozoic Era, opening the Cenozoic Era which
continues today.   As originally proposed by a team of
scientists led by Luis Alvarez, it is now ge