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RE: Giant Impact Near India - Does It Exist ???



And also that the KT extinction event had a single cause!  Sorry to keep
banging on about this, what with me not even being a palaeontologist or even
a geologist (but I did do Geology in my first year at uni).

It is a complex event and the only thing the mass extinctions that started
and finished the non avian dinosaurs is flood basalt.  A coincidence?

-----Original Message-----
From: Paul [mailto:bristolia@yahoo.com] 
Sent: 20 October 2009 14:27
To: dinosaur@usc.edu
Subject: Giant Impact Near India - Does It Exist ???

In "RE: Giant Impact Near India -- Not Mexico"
May Have Doomed Dinosaurs" it was written.

>On Tue, Oct 20th, 2009 at 5:57 AM, Mark Wildman  
><mwildman@saurian.org> wrote:  

>>I'm sort of curious here (extinction not a pet subject 
>>of mine), but if the > original Mexican impact was 
>>(allegedly) responsible for large global extinctions, 
>>and I believe that over 70% of all life was eliminated 
>>at the KT boundary, then the implications of a much 
>>larger asteroid hitting the planet at the same time, 
>>or even if there was a gap of a few hundred or a few 
>>thousand years, would, on the face of it, more or 
>>less eliminate life on earth. Survivors from the 
>>original impact struggling to recover, hit by a 
>> second catastrophe, would surely succumb? No?  

>Especially since India appears to have been in the 
>southern hemisphere at the  time. That would put a 
>large impact in both hemispheres, which would seem 
>to have left little in the way of a southern  refuge 
>(from which it's thought that extant birds owe their 
>ancestory).  

This discussion presumes that the so-called"Shiva 
Impact Crater" is a valid impact crater. At this 
time, planetary, structural, and other geologists
in general remained unconvinced that this is a valid 
impact crater. This is discussed in "New Dino-
destroying Theory Fuels Hot Debate" by Clara 
Moskowitz at;

http://www.space.com/scienceastronomy/091018-dinosaur-crater.html

For example, the article states:

"We have worked extensively throughout India 
and investigated a number of the localities 
where Sankar Chatterjee claims to have 
evidence of a large impact he calls Shiva crater," 
Keller wrote in an e-mail along with colleague 
Thierry Adatte of Switzerland's Universite de 
Neuchâtel. "Unfortunately, we have found no 
evidence to support his claims... Sorry to say, 
this is all nonsense.""

and

"As for the Shiva hypothesis, Gulick was very doubtful.

"There's a bunch of problems to say the least," Gulick 
said of Chatterjee's hypothesis. "There is no evidence 
g of it actually being a crater.""

David Rajmon, impact database at http://impacts.rajmon.cz/
and http://impacts.rajmon.cz/IDdata.html lists the "Shiva
Impact Crater" as a "Possible" impact structure with the
probability of it being an valid impact structure being less 
than 50 percent.

About the evidence for the this hypothesized impact crater,
the "Impact Database v.2009.2" states:

"Chatterjee et al. (2006) listed following lines of evidence 
for impact:

- Pseudotachylites ? two optical photographs showed dark 
veins in the basement granite described as aphanitic, micro- 
to cryptocrystalline material. One SEM photographs showed 
what was interpreted as pure silica glass referring to 
energy dispersive X-ray spectra (EDXS) data (not shown). 
Insufficient evidence was shown that the veins were 
melted and that they are actual pseudotachylites. Further, 
pseudotachylites form at various tectonic environments 
and do not constitute evidence for an impact.

- Rhyolite dikes ? no data were presented, only speculation 
that such rocks could have been formed by shock target melting.

- Geophysical anomaly ? presented a map of previously 
published low resolution gravity map with "15 mGal central 
anomaly and rising to +10 to +35 mGal in the "annular trough" 
and wetern central ring and up to +40 mGal towards the coast. 
It is speculated that the elongated positive gravity high 
in the west is related to an igneous complex, which is 
further speculated to be an impact melt. No evidence was 
presented such interpretation.

- Geothermal anomaly ? referred to a study that attributed 
high heat flow to crustal stretching possibly caused by 
a geodynamic even such as an impact. 

- Reference to reports of shocked quartz and geochemical 
anomalies from several K-T boundary sections in India ? 
extensive but entirely speculative discussion of the 
connection between these sections, impact induced melting 
and the Shiva structure."

Looking through the papers that are listed in "Paleogeographic 
maps for "Alleged World's B

http://dml.cmnh.org/2009Oct/msg00522.html and listed below, 
it looks like that the geology of the so-called crater is far, 
far more complicated than illustrated than in Chatterjee?s 
greatly simplified image of it. These references also provide 
plausible alternative, and admittedly prosaic, nonextraterrestrial 
tectonic origins for the structure, which Chatterjee interprets 
to be an impact crater.

For perspective, a good paper to read is:

Riemond, U. W., 2007, The Impact Crater Bandwagon (Some 
problems with the terrestrial impact cratering record)
Meteoritics & Planetary Science. vol. 42, No. 9, pp. 1467-1472.

Abstract at http://adsabs.harvard.edu/abs/2007M&PS...42.1467R 

PDF file at http://tiny.cc/ImpactBandwagon ,
http://articles.adsabs.harvard.edu/full/2007M%26PS...42.1467R , or
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2007M%26PS...4
2.1467R&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;file
type=.pdf 

More reference on geology and origin of the alleged impact 
crater:

Biswas S K 1982 Rift basins in the western margin of India
and their hydrocarbon prospects; American Association of
Petroleum Geologists Bulletin. vol. 66, no. 10, pp. 1497-1513.

Biswas S K 1987 Regional tectonic framework, structure and
evolution of the western margin basins of India.Tectonophysics,
vol. 135, no. 4, pp. 307-327.

http://dx.doi.org/10.1016/0040-1951(95)00020-N

Biswas, S. K., M. K. Rangaraju, J. Thomas, and S. K. 
Bhattacharya, 1994, Cambay- Hazad(!) Petroleum System in 
the South Cambay Basin, India: Chapter 37: Part VI. Case 
Studies--Eastern Hemisphere. In L. B. Magoon and W. G. Dow, 
eds., pp. 615-624. Memoir 60, American Association of 
Petroleum Geologists, Tulsa, Oklahoma.

Duncan, R.A., 1990, The volcanic record of the Reunion
Hotspot, Proceedings of the ODP, Sciences Results. vol 115,
pp. 3-9.

Duncan (1990) shows paleogeographic reconstructions.

http://www-odp.tamu.edu/publications/115_SR/VOLUME/CHAPTERS/sr115_01.pdf

Subrahmanya, K. R., 1988, Tectono-Magmatic Evolutio
ast of India. Gondwann Research. vol. l, no. 3/4, pp, 31 9-327.

http://dx.doi.org/10.1016/S1342-937X(05)70847-9

Sharma, K. K., 2007, "Cretaceous-Tertiary Tectono-Magmatism
in the NW Indian shield: A fragmenting continent."

http://www.mantleplumes.org/NWIndia.html

http://www.mantleplumes.org/WebpagePDFs/NWIndia.pdf

Todal, A., and O. Edholm, 1998, continental margin off Western
India and Deccan Large Igneous Province. Marine Geophysical
Researches. vol. 20, no. 4, pp. 273-291

http://www.springerlink.com/content/g7l126p314673055/

Additional references can be found in "Paleogeographic 
maps for "Alleged World's Biggest Impact Crater (India)" 
at http://dml.cmnh.org/2009Oct/msg00522.html

Yours,

Paul V. Heinrich
Baton Rouge, LA