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Impact/Extinction Refs (Long)



Hello everyone,

Here's a few papers that appeared in the last three issues of Geology and
last issue of Geotimes for those who are interested and/or are keeping up
with the subject.

First:
Chesapeake impact crater confirmed.  Geotimes,  December, 1995 p.10

This is just a  blurb reprinted from Science (v.269, Sept.22, 1995, p.1672)
but it appears that the the structure in the lower Chesapeake bay is of
impact origin according to Poag et al.  This is based on a study of the
gravity anomaly of the structure that supplements his earlier seismic
study.There was a flurry of press attention in the Maryland/Virginia area
when this was announced and Poag believes that the Bay may have formed
because of the impact 35 Ma. Great! Now I have a crater in my own back yard!
Good fishing there too!

See also;

Poag W. et al,  1994,  Meteoroid mayhem in Ole Virginny: Source of the North
American tektite field. Geology, v.22, no.8 , p.691-694. 
Note: That figurre 3 is a large folded chart detailing the crater in terms of
seismic profile.
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Eshet, Y., Rampino, M. R., and Visscher, H., 1995, Fungal  event and
palynological record of ecological crisis and recovery  acrosss the
Permian-Triassic bounary. Geology, v.23, no.11, p.967-970

Another  interesting paper that reports a "spore spike" at a critical
extinction boundary. Sounds a little like the "fern spike"  found at the K-T
bounday...

Also in the same volume;

Leroux, H., Warme, J. E.,  and Doukhan, J-C.,  1995, Shocked quartz in the
Alamo Breccia, southern Nevada: Evidence for a Devonian impact event.
Geology, v.23, no.11,  p.1003-1006

It seems that evidence is building for another impact induced extinction even
older than the K-T.
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Ward, W. C.,  Keller, G., Stinnesbeck, W., and Adatte, T.,1995,  Yucatan
subsurface stratigraphy: Implications and constraints for the Chicxulub
impact. Geology, v.23, no.10, p.873-876

Another interesting paper where the authors accept the structure's impact
origin but cannot conclusively state that it is of K-T age and may be
slightly older based on biostratigraphic studies.

Also,
Hurlbert, S. H., and  Archibald, J. D.,1995,  No statitistical support for
sudden (or gradual) extinction of dinosaurs. Geology, v23, no10, p.881-884
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Hollis, C. J., Rodgers, K. A., and Parker, R. J.,1995,   Siliceous plankton
bloom in the earliest Tertiary of Marlborough, New Zealand, Geology, v23,
no.9,  p.835-838

Authors report no radiolarian mass extinction across the K-T boundry of New
Zealand but rather an increase of these and diatoms and attribute this to
enhanced upwelling resulting from climatic cooling of the latest Cretaceous
and abrupt sea level changes as well.

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Hope this is of use.

Regards,
Thomas R. Lipka
Paleontological/Geological Studies