| Subject: Re: Did dinosaurs die from a meteorite impact or volcanism? |
Author:
Blobrana
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Date Posted: 09:36:12 11/19/04 Fri
In reply to:
Blobrana
's message, "Re: Did dinosaurs die from a meteorite impact or volcanism?" on 09:29:52 11/19/04 Fri
>November 19th:
Startling new evidence from boreholes drilled into the 120-mile-wide Chicxulub crater in Mexico indicate that the great impact, happened 300,000 years too early to have been the one that wiped out the dinosaurs.
The discovery comes at a time when some geologists are convinced that the Chicxulub event killed 70 percent of living species at the Cretaceous-Tertiary (K-T) boundary, 65 million years ago.
Several lines of geological evidence from Chicxulub make a compelling case for the crater having been formed too early to be the mass killer.
Evidence, broken `breccia` rocks, from a borehole, Yaxcopoil 1, was expected to provide final, irrefutable confirmation of Chicxulub's role in the K-T boundary mass extinction. It didn't.
On top of the impact breccia is about two feet of gently-laid-down, thinly layered seafloor mud built up over 300,000 years, Keller said. Those two feet of post-impact mud have the fossils, carbon isotopes and magnetic signal of the late Cretaceous, before the mass die-off.
It's 300,000 years too early .
Also missing from the Yaxcopoil 1 borehole rocks is any significant iridium signal , the extraterrestrial element that first clued scientists into the fact that an asteroid might have caused the K-T extinctions.
As to what really caused the K-T mass extinction; it was probably another asteroid impact combined with intense volcanic activity., and, many dinosaur researchers suspect that dinosaurs were on the decline before the final mass extinction.
Chicxulub might have played a role in their extinction. but a second impact, still undiscovered, might have been the terminal blow.
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