RE: New date for Chicxulub?

["Hope, Sylvia" <shope@calacademy.org>]

Highly recommended reading:

Smit, J. 1999. The global stratigraphy of the Cretaceous-Tertiary boundary
impact ejecta.  Annual Review of Earth and Planetary Sciences 27:75-113.

- SH 

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On
> Behalf Of Tommy Tyrberg
> Sent: Thursday, April 06, 2006 9:35 AM
> To: david.marjanovic@gmx.at; DML
> Subject: Re: New date for Chicxulub?
> 
> At 15:44 2006-04-06, David Marjanovic wrote:
> >>The above claim that the data in support of a direct relationship
> between
> >>the spherules and the iridium layer "doesn't make sense" seems
> much ado
> >>about nothing.
> >
> >Better yet: The GSA abstract doesn't mention any radiometric
> dating. So
> >when there are several spherule layers plus the boundary spread
> over 10 m,
> >why can't they all (except the lowest), including the boundary, be
> reworked?
> 
> 
> Or even more likely the whole ensemble formed in something more like
> 300
> minutes than 300,000 years. This seems to be yet another case of
> chronic
> gradualism. It seems that many geologists simply cannot conceive
> that near
> a 200 km impact crater in the hours after the impact sediments might
> *not*
> settle out slowly and peacefully in neat stratigraphic order.
> 
> It is worth noting that outside the Caribbean area nobody has ever
> found
> any trace of "multiple impacts" or that the impact layer is 10
> meters below
> the K-T boundary.
> 
> Tommy Tyrberg
> 
>