New Study: Deccan, not Chicxulub, Killed Dinos

[Schneibster]

New studies of the geohistory of the Deccan Traps megavolcano eruptions in India 65 million years ago have shown that the climate changes spurred by the vast quantities of CO2, sulphur dioxide, and ash released into the atmosphere as over half of the Indian subcontinent was covered by lava flows that went on for some 35 thousand years were sufficient by themselves to cause the KT mass extinction. Until now, there had not been sufficient evidence to overturn the Chicxulub asteroid impact as the culprit, but more exact and deeper study of the geology of the Deccan Traps and the surrounding regions' paleobiology, specifically of foraminifera species diversity, has shown that the impact of the eruption was overall much larger than that of any impactor including Chicxulub.

Current thinking is that the combination of the two, potentially along with other impacts one of which was found not far from the Deccan, was the reason that the mass extinction was raised to the status of one of the two worst in Earth's history.

It is worthy of note, however, that this is an ongoing controversy. A panel of paleontologists came down on the side of the impact theory in 2010, and there has not yet been adequate time for criticism of the latest Deccan data. So this will be an ongoing story.

Science Daily has a pretty good article on the controversy and the latest evidence here. Enjoy.

[Tero]

Sounds reasonable.

I was never a meteor fan.

[Horwood Beer-Master]

Are they speculating that without Chicxulub the impact of the Deccan eruptions would have eventually killed off all the KT victims, or are they saying that the vast bulk of these species in fact were extinct prior to Chicxulub?

If it's the former than surely we must still declare Chicxulub the killer. I mean if you're beaten to within an inch of your life and then shot in the head, your cause of death is still is the gunshot wound, not the beating - even if you most likely would have died in the end if you'd just been left there.

[Don't Panic]

Anyone put out the theory that the impact caused the eruptions?

[Schneibster]

Are they speculating that without Chicxulub the impact of the Deccan eruptions would have eventually killed off all the KT victims, or are they saying that the vast bulk of these species in fact were extinct prior to Chicxulub?

I don't think they have gotten that far. They've said so far that the impact of the Deccan eruptions was enough.

If it's the former than surely we must still declare Chicxulub the killer. I mean if you're beaten to within an inch of your life and then shot in the head, your cause of death is still is the gunshot wound, not the beating - even if you most likely would have died in the end if you'd just been left there.

False analogy; it's not one death, it's billions (and that's not counting foraminifera).

[Schneibster]

Anyone put out the theory that the impact caused the eruptions?

I don't think it's big enough.

ETA: IIRC the timing's right, though. Chicxulub happened before the second phase of Deccan I think. Part of the problem with associating it directly with the KT boundary is that it's a few hundred thousand years too early.

[JimC]

Anyone put out the theory that the impact caused the eruptions?

I don't think it's big enough.

ETA: IIRC the timing's right, though. Chicxulub happened before the second phase of Deccan I think. Part of the problem with associating it directly with the KT boundary is that it's a few hundred thousand years too early.

I'm sure I've read an account in NewScientist that suggested that the impact may have triggered a phase of Deccan, in the sense that if the magma build up was almost ready to blow, the impact could have tipped the balance...

[Schneibster]

I think I recall the same article.

[Horwood Beer-Master]

...

If it's the former than surely we must still declare Chicxulub the killer. I mean if you're beaten to within an inch of your life and then shot in the head, your cause of death is still is the gunshot wound, not the beating - even if you most likely would have died in the end if you'd just been left there.

False analogy; it's not one death, it's billions (and that's not counting foraminifera).

An analogy doesn't have to be perfect to be valid enough.

If the vast bulk of the KT victim species were still extant the day before Chicxulub, but most were extinct, say, 3 weeks later - then I'd think it was fair to say it were the bullet-in-the-head wot done it.

[Schneibster]

...

If it's the former than surely we must still declare Chicxulub the killer. I mean if you're beaten to within an inch of your life and then shot in the head, your cause of death is still is the gunshot wound, not the beating - even if you most likely would have died in the end if you'd just been left there.

False analogy; it's not one death, it's billions (and that's not counting foraminifera).

An analogy doesn't have to be perfect to be valid enough.

Unfortunately, this one doesn't qualify.

[Horwood Beer-Master]

...

If it's the former than surely we must still declare Chicxulub the killer. I mean if you're beaten to within an inch of your life and then shot in the head, your cause of death is still is the gunshot wound, not the beating - even if you most likely would have died in the end if you'd just been left there.

False analogy; it's not one death, it's billions (and that's not counting foraminifera).

An analogy doesn't have to be perfect to be valid enough.

Unfortunately, this one doesn't qualify.

Meaning?

[Don't Panic]

Anyone put out the theory that the impact caused the eruptions?

I don't think it's big enough.

ETA: IIRC the timing's right, though. Chicxulub happened before the second phase of Deccan I think. Part of the problem with associating it directly with the KT boundary is that it's a few hundred thousand years too early.

I'm sure I've read an account in NewScientist that suggested that the impact may have triggered a phase of Deccan, in the sense that if the magma build up was almost ready to blow, the impact could have tipped the balance...

I was thinking that it's pretty much the other side of the world, shock waves hitting a weak point from multiple directions at once.

[Gawdzilla Sama]

Anybody care to speculate on how long the "nuclear winter" was, if it happened? If the planet was in trouble from the Deccan, the asteroid impact would make it worse. Same thing if the sequence is reversed. So a nuclear winter would be bad, but for how long.

My guess is less that three years, because that's how long the reptilians that survived would be able to hibernate.

[Faithfree]

Why doesn't it surprise me that Gerta Keller is involved.

I should explain that in a previous life in academia I did lots of research on impact-related stuff and got very familiar with the K-T mass extinction, although I didn't work on that specifically. I think impact as the main cause is a very water tight case, but of course I'm always open to new evidence so it would be interesting to read the actual paper rather than the media hype. The debate about the involvement of the Decan Traps has been very long, very tedious, and previously always toothless, but I'd like to see what the new paper has to offer. Though I doubt I'll be convinced.

[Schneibster]

Why doesn't it surprise me that Gerta Keller is involved.

I should explain that in a previous life in academia I did lots of research on impact-related stuff and got very familiar with the K-T mass extinction, although I didn't work on that specifically. I think impact as the main cause is a very water tight case, but of course I'm always open to new evidence so it would be interesting to read the actual paper rather than the media hype. The debate about the involvement of the Decan Traps has been very long, very tedious, and previously always toothless, but I'd like to see what the new paper has to offer. Though I doubt I'll be convinced.

The evidence sounds pretty good in this case. There are and have always been timing problems between the Chicxulub event and the beginning of the extinction event in the geological record. And the study of plankton is pretty definitive that there were big problems for a much longer time than the single asteroid strike can explain.

Journal References:

G. Keller, T. Adatte, S. Gardin, A. Bartolini, S. Bajpai. Main Deccan volcanism phase ends near the K–T boundary: Evidence from the Krishna–Godavari Basin, SE India. Earth and Planetary Science Letters, 2008; 268 (3-4): 293 DOI: 10.1016/j.epsl.2008.01.015
B. Gertsch, G. Keller, T. Adatte, R. Garg, V. Prasad, Z. Berner, D. Fleitmann. Environmental effects of Deccan volcanism across the Cretaceous–Tertiary transition in Meghalaya, India. Earth and Planetary Science Letters, 2011; 310 (3-4): 272 DOI: 10.1016/j.epsl.2011.08.015

I embedded the links.