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Big Craters

Message text written by INTERNET:STARSONG@prodigy.net
>I would appreciate it if you will provide us with a reference or
references (i.e., from peer-reviewed scientific journal or journals)
substantiating this claim of an impact sites ("rivaling the Yucatan crater
in size with NO associated extinctions..."), naming the impact
location(s), and breifly describing the criteria by which the structure(s)
are determined to be of an impact nature?<

        Ya gotta love the subtle undertones of this post (NOT!)...but I'll
respond anyway.

NAME OF CRATER:  Morokweng
LOCATION:  southern Africa
AGE:  at or very near Jurassic-Cretaceous boundary (with which no mass
extinctions are associated)
CRITERIA ON WHICH IT IS BASED:  mostly seismic and gravity anomaly (crater
is subsurface), but also petrologic and geochemical
SIZE OF CRATER:  340 km (~154 miles) diameter

Koeberl, C., Armstrong, R.A., and Reimold, W.U.  1997.  Morokweng, South
Africa:  a large impact structure of Jurassic-Cretaceous boundary age. 
_Geology_ 25(8):  731-734.

Corner, B., Reimold, W.U., Brandt, D., and Koeberl, C.  1997.  Morokweng
impact structure, Northwest Province, South Africa:  geophysical imaging
and shock petrographic studies.  _Earth and _Planetary Science Letters_
146:  351-364.

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                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 899-2809
                  Fax: ; (505) 841-2866