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Re:Paleocene Dinosaurs



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Forwarded message:
Subj:    Re: Paleocene Dinosaurs
Date:    97-09-10 16:25:57 EDT
From:    MBell16766

To:      Steve.Tomporowski@us.ms.philips.com

Steve Tomporowski asks about the dinosaur remains in the Bug Creek stream
channel deposits deposited (at least in part) in the Paleocene. Unless a
dinosaur specimen is found at least partially articulated in Paleocene
deposits a post Cretaceous non-avian dinosaur will never be accepted. Teeth
and isolated skeletal elements just will not serve as adequet evidence. These
isolated bits of material that get mixed up with fossils from a completely
different time via erosion are called "rework" in the business. Reworked
material.
Postdinosaur (but only by a couple of thousands of years) streams in the
Paleocene probably cut through dinosaur-rich deposits of the Hell Creek
Formation, teeth and bones spilled from the banks and were later re-deposited
in the Paleocene streambeds.
Arguments have been made about the pristine condition of the dinosaur teeth
found in these deposits. But tests in lapidary tumblers have shown very
little wear on dinosaur teeth, even after several hundreds of simulated miles
of travel (was that one of those Farlow papers?).
In the field, I've seen many instances of this happening. In fact, if you
would like to see this at work, go to Badlands National Park. Find a place
where the Interior Paleosol is exposed. This is the soil surface that many of
the famous Badlands mammals lived on. But the soil is actually the Pierre
shale, home of mosasaurs and plesiosaurs from the end of the age of
dinosaurs. Titanotheres and three-toed horses stepped on mosasaur fossils
when they came down to their streams to drink.  
Just south of Badlands National Park, a Pleistocene mammoth kill site was
found associated with Eocene/Oligocene fossils.
I'm sure that others on the list who have spent time in the field could tell
many stories about reworked fossils. It really happens a lot more than one
would expect.
Dan Varner.