[Rockhounds] Trip Report - Denver Area

[Pmodreski at aol.com]

Hi Axel (and the List),
 
This locality--very accessible, it's a roadcut on a frontage road on the  
south side of US-285 just south of Morrison, Colorado, on the southwest side of  
the Denver metro area--is very interesting.  The Dakota Sandstone here  
(Cretaceous age) is saturated with oil, and it does fluoresce very well in UV  
light, a whitish color (yellowish-white I think; I haven't looked at a sample in  a 
while), LW and SW.  The sandstone where it contains oil is, as you see  when 
the break off a fresh piece, dark brownish-colored due to the oil, and you  
can smell the oil too; but on exposed weathered surfaces of the roadcut, the oil 
 deteriorates, and the surface of the sandstone becomes  stained 
chalky-whitish or greenish-yellow from the degradation products  (not fluorescent) of the 
oil.  A separate material, seeping mostly out of  drill holes (left rom making 
the roadcut) in the sandstone, is black tarry  natural asphalt, and Kreigh 
collected a sample of this.  As I recall,  however, the black asphalt is not 
fluorescent.
 
This site is the best example I know of, of an "uplifted actual oil field"  
where you can look at the rock "live"!
 
Cheers,
Pete Modreski



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