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Re: All kinds of odd observations
From: email@example.com (David Brez Carlisle)
> Terry also queries the relevance of iridium. This is now
> recorded from over a hundred sites in the K-T boundary rocks from
> all continents and from deep-sea cores. Even though Alvarez et
> al. only had th ree sites for their original paper they guessed
> right that it would turn out to be world-wide.
True. However the interesting thing is that at *some* sites there
appear to be several iridium spike, rather than just one. (This
is variable from site to site, but still notworthy).
> BITING BY SAUROPODS
> Peter Buchholz has doubted that a bite by a sauropod could be
> much of a deterent. Paul Willis has pointed to the bite of a
The error in this analogy is that a wombat, like most mammals,
does a fair bit of chewing. Sauropods used their teeth mainly for
collection of leaves - their mouths were not built for chewing.
Thus they lacked the "grinding" teeth of a wombat (or a human
- a human bite is *quite* nasty).
Now the herbivorous dino *I* would hate to be bitten by is Triceratops,
since its jaw closing muscles were *enormous*
> Th e nearest any dino fossil has been found to the
> K-T boundary is 2 meters.
This is no longer true. Isolated dino bones have been found within
a few inches of the boundary. (And teeth have been found up to
and *past* the boundary - but these may be reworked).
> CRETACEOUS SEDIMENTS INSIDE CHICXOLUB CRATER
> Any crater more than about 4 miles across is a complex
> crater. The Barringer Crater in Arizona is perhaps as large
> as any simple crater we can expect to see. An i mpact causing
> a crater larger than this will produce a complex c rater with
> a central uprising and slumped walls. Chicoxolub (I never can
> spell that) has two main rings, the more marked one 180 km.
> across and a fainter one, 300 km. Alan Hildebrand (Geol.
> Survey of CAnada) does not believe th at the 300 km ring is of
> any great significance and p uts the primary diameter at about
> 182 km. In any case there are slumped rocks throughout, where
> the walls have collapsed. Since these were late Creteceous,
> then of course all blocks (many of which remain intact in such
> slumps - see Richard Grieve's papers--one good general account
> is in Scientific American about 1988) were cretaceous in age.
> Any drilling i nto th ese blocks would show a late Cretaceous
> age, espceially in the outer ring.
Hmm, I need to check the note to see if the cores were central
or peripheral, and what the position of the sediment was relative
to the melt layer. (Could a slump block, or its equivalent,
get *under* the melt layer??)
I certainly agree that a large, intact slump block could be explanation.
> The only true criterion for the age of the crater is the
> radiometric age of the MELT at the bo ttom of the crater.
> Two teams have now dated this - the Berkeley group and the
> Geol. Survey of Canada team. Both agree that the melt
> dates to between 64 and 65 Ma. Both have also found late
> Cretaceous dates from the breccia that overlies the melt.
As I said - my preference right now is that the Chicxulub crater
*is* the boundary impact, I am just unwilling to call the case
closed until it is verified that the sediments found *were* a
The peace of God be with you.