GSA Paper Demonstrates Single Impact at Cretaceous-Tertiary Boundary

Paul bristolia at yahoo.com
Mon Apr 2 08:28:10 EDT 2007

Dear friends,

There is a new paper on the impact and extinction
at the Cretaceous-Tertiary Boundary. It is:

MacLeod1, K. G., Whitney, D. L., , Huber, B. T.,
and Koeberl, K., 2007, Impact and extinction in
remarkably complete Cretaceous-Tertiary boundary
sections from Demerara Rise, tropical western
North Atlantic. Geological Society of America.
vol. 119, no. 1, pp. 101-115.

http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FB25955.1

They found a single, about 2-cm thick, layer of
spherules, which is interpreted to a primary air-
fall deposit. They found no other spherule layers
in the multiple cores of the K-T boundary section,
which were recovered.

They concluded:

"Sedimentological, geochemical, and paleontological
changes across the boundary closely match patterns
expected for a mass extinction caused by a single
impact."

Best Regards,

Paul
Baton Rouge, LA

New Paper in Chicxulub - K-T Boundary Controversy Published

Paul bristolia at yahoo.com
Tue Mar 13 08:36:08 EDT 2007

Dr. Gerta Keller and coauthors have published another paper
about their hypothesis that the Chicxulub impact predates
K–T boundary. This time, they reinterpret the K-T Boundary
found exposed along and near the Brazos River in Texas.

The paper is:

Keller, G., T. Adatte, Z. Berner, M. Harting, G. Baum, M.
Prauss, A. Tantawy and D. Stueben, 2007, Chicxulub impact
predates K–T boundary: New evidence from Brazos, Texas.
Earth and Planetary Science Letters. vol. 255, no. 3-4 , 30
pp. 339-356. doi:10.1016/j.epsl.2006.12.026

The link to the abstract can be found at:

http://www.sciencedirect.com/science/journal/0012821X

Best Regards,

Paul H.