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Wabar Crater ages (was: Bronze Age Catastrophes)

Okay, here's the deal on Wabar from Jeff Wynn (jwynn@usgs.gov):

The paper with Shoemaker is in review, and under some negotiation
with regard to its final publication place, so I can't give a ref.
You can check out the abstract by Shoemaker and Wynn (Lunar and
Planetary Sci. 28, 1313-1314 (1997), or, if you have Adobe Acrobat
reader, it's at: 
   http://cass.jsc.nasa.gov/meetings/lpsc97/pdf/SESS37.PDF.
This mentions the probable young age.  You can also check out
   http://minerals.er.usgs.gov/emrst/wynn/3wabar.html 
for a short paper that does not mention much about the age.  

The latest evidence for a young age is:
   1) New thermoluminescence dates on the sands underlying the craters
      give <600 years.
   2) The craters are supported by an extremely fragile rim
      structure that seems unlikely to have survived 1000's of years.
   3) The largest crater has shallowed from 12 m deep in the
      1930's, to 5-8 m in the 1960's to 1-3 m in the 1990's,
      and so, by extrapolation, it is unlikely that it could be 
      very old.
   4) A bright bolide (called "the Nejd") accompanied by sonic
      booms was seen over Riyadh in spring, 1863, headed exactly in 
      the direction (SE) of the present Wabar craters.  The distribution
      of ejecta around the crater is consistent with a low-angle
      impact from the northwest.  

-Jeff Grossman
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