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RE: Chicxulub's Antipode (Re: cause of death at KT)

I can't put my hand on the reference at the moment, but I saw a very
interesting paper in the early 90's proposing that the antipodes to the K-T
impact was near the west coast of India at the time, and the convergence of
shock waves ruptured the crust and instigated the flood basalts (Deccan

Ah, I see there was some discussion of this on the list in '95, e.g.

As pointed out in that post, the time and place seem to be far enough out
that it isn't likely.
Dr John D. Scanlon
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au

> -----Original Message-----
> From: Phillip Bigelow [mailto:bigelowp@juno.com]
> Sent: Saturday, September 02, 2006 5:33 AM
> To: dinosaur@usc.edu
> Subject: Chicxulub's Antipode (Re: cause of death at KT)
> On Fri, 01 Sep 2006 22:09:18 +0200 David Marjanovic
> <david.marjanovic@gmx.at> writes:
> > > The antipodes would probably be worse. There is a strong
> > concentration
> > > of re-entering debris there, and it will all be moving at orbital
> > speeds,
> > > so
> > > anything living there is likely to be fried.
> > What would have been at the antipodes?
> AFAIK, the best guess is open sea.
> Modern coordinates of Chicxulub:  21.33 degrees N; 89.5 degrees W
> Modern anitpode of Chicxulub:   21.33 degrees S; 90.5 degrees E (which is
> presently occupied by a lot of sea water)  But was a land mass there 65
> mya?  I made a quick perusal of the DML archives, and it appears that the
> our current knowlege of latest Maastrichtian plate movements and relative
> plate positions place no major land mass at the antipode.
> Regarding what type of effects one might have witnessed at the antipode:
> - Tsunamic effects would have been minor, because North and South America
> would have blocked the waveform from the paleo Pacific and Tethys Oceans.
>  Europe and Africa would have blocked the waveform from entering from the
> opposite direction.
> - What about reentering ejecta?  It was probably no worse than elsewhere
> on the globe.  Keep in mind that just because some material went
> suborbital or fully orbital doesn't *require* that the material must fall
> at the antipode.  It could fall just about anywhere on Earth, which is
> dictated by the ejecta's altitude (ejecta in low Earth orbit will reenter
> sooner; higher orbits may take hundreds of years to degrade to reentry).
> - Seismicity:  Now *those* effects would have been interesting (that is,
> if the antipode was part of a land mass.....which it apparently wasn't).
> In addition to the P-Wave arrival, which would have been brutal (imagine
> the earth beneath your feet throwing you up in the air about a third of a
> meter), there would have been some righteously bitchin' S-Waves which
> would be coming toward you from every azimuth.
> So if you were standing on land, you would first have been thrown up in
> the air by the P-wave, and then shortly thereafter, you would have been
> thrown in every lateral direction radomly, probably quite violently, by
> the S-waves.  [What DO converging S-waves do to bedrock?  I'll bet that
> is an understudied topic in geophysics and structural geology!]
> Has anyone thought of the following:
> Let's assume for the sake of argument that the Chicxulub antipode was
> occupied by sea floor rather than by dry land. Is this part of the sea
> floor still preserved?  If it is, and if the site can be located, would
> it would be worthwhile to drill into into it and see what types of
> faulting patterns characterize a mega-converging seismic event at an
> antipode?
> I'm thinking of the structural geology seen at the antipode of the
> Caloris [impact] Basin on Mercury and the structural geology seen at the
> antipode of the Stickney Crater on Phobos.  Not to mention the antipodal
> structures on Mimas.
> <pb>
> --