Giant impact near India -- not Mexico -- may have doomed dinosaurs

Oct 15, 2009
This diagram shows a three-dimensional reconstruction of the submerged Shiva crater (~500 km diameter) at the Mumbai Offshore Basin, western shelf of India from different cross-sectional and geophysical data. The overlying 4.3-mile-thick Cenozoic strata and water column were removed to show the morphology of the crater. Credit: Sankar Chatterjee, Texas Tech University

A mysterious basin off the coast of India could be the largest, multi-ringed impact crater the world has ever seen. And if a new study is right, it may have been responsible for killing the dinosaurs off 65 million years ago.

Sankar Chatterjee of Texas Tech University and a team of researchers took a close look at the massive Shiva basin, a submerged depression west of India that is intensely mined for its oil and gas resources. Some complex craters are among the most productive hydrocarbon sites on the planet. Chatterjee will present his research at this month's Annual Meeting of the Geological Society of America in Portland, Oregon.

"If we are right, this is the largest crater known on our planet," Chatterjee said. "A bolide of this size, perhaps 40 kilometers (25 miles) in diameter creates its own tectonics."

By contrast, the object that struck the Yucatan Peninsula, and is commonly thought to have killed the dinosaurs was between 8 and 10 kilometers (5 and 6.2 miles) wide.

It's hard to imagine such a cataclysm. But if the team is right, the Shiva impact vaporized Earth's crust at the point of collision, leaving nothing but ultra-hot mantle material to well up in its place. It is likely that the impact enhanced the nearby Deccan Traps that covered much of western India. What's more, the impact broke the Seychelles islands off of the Indian tectonic plate, and sent them drifting toward Africa.

The geological evidence is dramatic. Shiva's outer rim forms a rough, faulted ring some 500 kilometers in diameter, encircling the central peak, known as the Bombay High, which would be 3 miles tall from the ocean floor (about the height of Mount McKinley). Most of the crater lies submerged on India's , but where it does come ashore it is marked by tall cliffs, active faults and hot springs. The impact appears to have sheared or destroyed much of the 30-mile-thick granite layer in the western coast of India.

The team hopes to go India later this year to examine rocks drill from the center of the putative crater for clues that would prove the strange basin was formed by a gigantic impact.

"Rocks from the bottom of the crater will tell us the telltale sign of the impact event from shattered and melted target rocks. And we want to see if there are breccias, shocked quartz, and an iridium anomaly," Chatterjee said. Asteroids are rich in iridium, and such anomalies are thought of as the fingerprint of an impact.

More information: View research abstract, at gsa.confex.com/gsa/2009AM/fina… /abstract_160197.htm

Source: Geological Society of America

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dcoder
3 / 5 (2) Oct 15, 2009
Loodt
2.9 / 5 (9) Oct 15, 2009
The comment ...some complex craters are among the most productive hydrocarbon sites on the planet... is most intriguing. Does this tie-in with the Russian theory that hydrocarbons are produced in the Mantle and that oil fields are not microorganism based in genesis? Are there any further references that can be used for background reading?
Nik_2213
4 / 5 (6) Oct 15, 2009
Is there anywhere that evidence from both impacts might be found to identify interval and succession ? I must wonder if these hit a dozen hours, a dozen years or a dozen millenia apart...
gwrede
2.6 / 5 (10) Oct 15, 2009
I always thought that large oil deposits are hardly the result of died organisms. Then I read that Saturn's moon Titan has open lakes filled with hydrocarbons. It'll take a lot of explaining before I believe that they come from died organisms.
Caliban
2.8 / 5 (4) Oct 15, 2009
@Loodt-
You might try a search for "rock oil" regarding petrogenetic hydrocarbons.
Another item not mentioned in this article is the co-incedence of gold, silver, and rare-earth elements associated with these impact basins. Could be quite a boon for India.
nkalanaga
4.3 / 5 (4) Oct 15, 2009
Nik: It wouldn't be surprising if they are related. Astronomers are finding that many asteroids are binary, and a combination of 40 km and 8-10 km asteroids would be quite plausible. It would be less likely that two of the biggest dated impacts happened at almost the same time and WEREN'T related.
out7x
4 / 5 (4) Oct 16, 2009
Nothing said here about timing of the event. Chicxulub has the problem of event timing. Deccan traps are closer to end-cretaceous.
QubitTamer
Oct 16, 2009
This comment has been removed by a moderator.
QubitTamer
4.5 / 5 (2) Oct 16, 2009
i for one have always believed that there is / was plenty of abiogenic leftover hydrogen and carbon from the stellar explosion (nova or supernova) event which gave birth to our current solar system to explain the oil deposits on earth anhttp://www.livesc...ins.html of course all petrogeologists will vehementally disagree, but then ask yourself how the earth can be so full of all of the other elements of the periodic table and not just be chock full of C and H in the exact chemical and ionic configurations for them to form pools of oil all throughout the crust and mantle. if we can find and mine au ag and everything else, why shouldn't complex hydrocarbon chains also be available. the russians have been way ahead of the thinking in this field for years.
Au-Pu
2.7 / 5 (6) Oct 16, 2009
Sorry to be a wet blanket.
Whether the Yucatan and the Deccan impacts were related or not and whether they both contributed to the KT boundary deposit is not my concern. But the relationship of these events to the extinction of the dinosaurs is of interest to me. Had either of these two events or both in combination been responsible for the extinction of the dinosaurs one would expect that some of the larger dinosaur bones would have been in contact with the KT boundary or even more probable some of the larger specimens would have had their bones protruding through the KT boundary.
Even if it took 5 or 10 years for the iridium to settle out of the atmosphere and form the KT boundary it would take a vastly greater time for these giant bones to be covered by dust or other sediments and in the meantime rains would have washed much of any atmospheric deposition off those exposed bones.
Yet to the best of my knowledge every dinosaur relic has been found below the KT boundary.
to end later
Au-Pu
2.4 / 5 (5) Oct 16, 2009
To continue,
It has to be possible that dinosaurs had become extinct long before the major impacts that created the KT boundary.
This could quite easily have occurred with the arrival of flowering plants. If these proliferated at a very rapid rate and quickly supplanted the natural diet plants of the herbivores, too quickly for them to adapt to the change then they would have died out. The demise of the herbivores would have very quickly lead to the demise of the carnivores.
Should small numbers have made the transition to flowering plants they would have been too few to survive the dietary needs of the carnivores with the extinction of the bulk of the herbivores.
Because of the close proximity in time between the two events the idea of a mass extinction being caused by such an impact appears to have too much appeal for anyone to look beyond such an event as THE cause. The mass extinction of other life forms may well have been caused by such impacts and their aftermath.
Ronan
5 / 5 (1) Oct 17, 2009
Au-Pu: That might make sense, except that the event that you're referring to (the sudden spread of flowering plants) happened ~100 MYA; 35 million years before the K-T extinction. Some dinosaurs might have had trouble adapting, but obviously they were pretty okay for the next 35 million years.

As for your surprise at no fossils specifically straddling the K-T layer...that's expecting a little much, isn't it? I mean, think about it. If you take a population of animals during a mass extinction, and during a "normal" period in Earth's history, after a hundred years they're both (almost) all going to be dead. The deaths are nastier and no descendants are left during a mass extinction, but other than that the total number of deaths are the same, and there's no real reason to expect a spike in fossils--and to have one right on the boundary would be a colossal stroke of luck.
Paradox
not rated yet Oct 17, 2009
Unless these events happened fairly close together, you would think that someone would have found two separate iridium layers.
Yogaman
3 / 5 (2) Oct 17, 2009
Binary asteroid really seems much more likely, but could Shiva be the "exit wound" of Chicxulub?

Scene: Ancient Galactic Future Membership Council reviews its efforts to eradicate Earth's dinosaurs because they are viewed as a dead end that will never evolve into the kind of members the council wants. Unfortunately, the asteroid bullet - "straight through the planet" for special effects impact on the big screen - was only partially successful. To remedy, Council authorizes Deccan fumigation. Plot follows heroic efforts of crew to light and get away.
nkalanaga
not rated yet Oct 19, 2009
There was a theory several years ago similar to that, but without the aliens. The idea was that the surface shock traveled around Earth in all directions, and focused at the point opposite the impact. The theory is sound, but whether it could trigger massive vulcanism was hotly debated.
Yogaman
not rated yet Oct 20, 2009
nkalanaga: Acoustic shock wave theory is 'sound' and massive vulcanism is 'hotly debated.'

It took me a moment to recognize your brilliant wordplay, but thank you very much.