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Re: three impacts at the K-T boundary



>From: "Mike Hoffmann" <Mike.Hoffmann@mch.sni.de>

>> An additional thought - consider the scale of some of the Jupiter strikes. 
>> Many of them were vastly more powerful than anything which struck during
>> the Phanerozoic (540 Mya to the present).  If just one of the larger of
>> them had struck the Earth, it would have produced a crater which extends
>> from Washington, D.C. to New York City, and probably have boiled the oceans
>> to a vapor in the process.  So much for multicellular life...
>
>I think I remember it discussed that the SL9 impacts would have not hit as
>violently on Earth as they had on Jupiter: apparently simple physics, with
>Jupiter accelerating the chunks to a *lot* higher velocities.
>
>The size of the SL9 "rocks" by themselves would fit the regular K-T strike
>theory quite well. Sorry, meaning a *multiple* strike theory.

Hmm, then we're a little safer...

In any case, here are the references I mentioned:

Meyerhoff, A.A., J.B. Lyons, and C.B. Officer.  1994.  Chicxulub Structure:
A volcanic sequence of Late Cretaceous age.  Geology (forgot to check
volume number, but is the current 1994 volume):3-4.

Izett, G.A., W.A. Cobban, J.D. Obradovich, and M.J. Kunk.  1993.  The
Manson impact structure: 40Ar/39Ar age and its distal impact ejecta in the
Pierre Shale in southeastern South Dakota.  Science 262:729-732.

As for Deccan stratigraphy, look for almost any paper on Indian
geology/paleontology/stratigraphy about the "intertrappen" beds.

Bibliographically yours,
                                     
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092

email:  tholtz@geochange.er.usgs.gov 
Phone:  703-648-5280
FAX:            703-648-5420