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RE: Gastroliths



Norm intended to post this, so I am forwarding it.

> -----Original Message-----
> From: Stanley Friesen [SMTP:sarima@ix.netcom.com]
> Sent: Thursday, April 08, 1999 12:07 AM
> 
        (quoting me):
> >  The limy deposits I am familiar with
> >formed on shallow lake beds, and they were often hypersaline, complete
> with
> >algal stromatolites.
> 
> Another *possible* source for limey deposits in a semi-arid zone like, the
> Morrison area 130 MYa, is caliche, that is pedogenic processes.  I cannot
> say that such exists  in the Morrison, but it would not surprise me if it
> did.
> 
> 
        I have seen what appeared to be a caliche layer in the Morrison west
of Grand Junction, CO near the Riggs Brachiosaurus quarry, although I admit
to not having done a thorough petrologic analysis of it.  It's simply a good
candidate, and I agree that the Morrison is likely to contain caliche.

        Pedogenic carbonate nodules are ubiquitous in the Morrison, but they
are dispersed within the paleosols rather than forming solid layers.  These
may include the "kunkar" nodules referred to by Bakker in Dinosaur Heresies,
but the ones I've seen are developed to varying degrees.  In other words,
while some nodules have concentric structure and are clearly distinct from
the enclosing sediment, others are little more than "blebs" of calcareous
claystone which weathers to a granular texture due to their presence.  But
they confirm what Stan suggested--that much of the Morrison has been
affected by pedogenesis.

        Incidentally, stromatolitic limestone lake beds can be seen along
the access road within a mile or so of the visitor center at the
Cleveland-Lloyd Allosaurus quarry near Price, Utah.