In a message dated 9/19/01 7:15:55 AM Mountain Daylight Time,
gmurphy@raex.com writes:
<< Can any of the geologically knowledgeable on the list tell me
the best current estimates of the date of the Chicxlub event? I find
references to "about" 64 and 65 million years ago but also have "67"
rattling around in my head. I know geological dating isn't as precise
as spectroscopy but what's the best guess?
& a more trivial question: What's the preferred spelling? I
find Chicxlub spelled thus, but also with an extra u, Chicxulub.
Shalom,
George
George L. Murphy
http://web.raex.com/~gmurphy/
"The Science-Theology Interface"
>>
Hi George. I don't pretend to have kept up on all the Chicxulub studies but
after a quick check of current literature, even the most recent papers seem
to cite two references from 1992. Presumably no dating work since has
modified the results.
40Ar/39Ar dating of impact melt rock yields ages of 64.98 +/- 0.05 Ma
(=Mega-annum = million years ago) [Swisher et al., 1992] and 65.2 +/- 0.4 Ma
[Sharpton et al., 1992]. Also, K/T tektite-like glasses yield results of
65.07 +/- 0.10 Ma [Swisher et al., 1992]. The references are:
Swisher, C.C. and 11 others, 1992, Coeval 40Ar/39Ar ages of 65.0 Million
Years ago from Chicxulub crater melt rock and Cretaceous-Tertiary boundary
tektites: Science, v. 257, p. 954-958.
Sharpton, V.L., and 5 others, 1992, New links between the Chicxulub impact
structure and the Cretaceous/Tertiary boundary: Nature, v. 359, p. 819-821.
As you can see, "Chicxulub" seems to be the preferred spelling.
Hope this helps.
Karl
*************************
Karl V. Evans
cmekve@aol.com
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