End of the "Lone Asteroid" Theory?

hussar writes "This BBC article reports on research that suggests the dinosaurs were not killed off by the Chicxulub asteroid's immediate effects but ultimately fell to evironmental stresses caused by a second asteroid that hit about 300,000 years later. The second impact may have been in the Indian Ocean."

Comments

Re:Keller's Conclusions [weakly] Refuted

[H4x0r Jim Duggan]

Kellers findings are pretty well founded. The idea is that the Chicxulub impact occurred during this warming period with severe environmental effects but the extinction of the dinosaurs - When the second impact finally occurred, it hit an already stressed community which was the straw that broke the camel's back. Almost anything could have wiped them out at that point. Jan Smits doesn't refute this very clearly - but I would accept that the theory is less sensational that it appears from the headline.

Yet another theory?

[MissMarvel]

Ah.... The great K-T extinction debate continues....

For those interested in reading about the supporting data and possible causes of the K-T extinction,
here's a good discussion" by Dewey M. McLean of the Department of Geological Sciences,
Virginia Polytechnic Institute and State University.

He deals with that

[Von Rex]

Check out his reply to the original article.

There's a picture of the soil sample he's talking about, too.

"The best evidence in favour of a single impact, I repeat, is in the K/T record from the US western interior. In numerous outcrops from Alberta in Canada, through Dogie Creek in Wyoming to the Raton Basin in New Mexico an iridium-enriched clay layer occurs in coal swamp deposits at the palynological K/T boundary. This clay layer has a dual nature (Izett, 1990), and consist of two layers: a lower layer that contains spherules (best seen in Dogie creek (Fig. 7) morphologicaly indistinguishable from the Chicxulub spherules from the Gulf.

The upper layer is strongly enriched in iridium and shocked minerals, such as quartz, feldspar and zircons. The shocked zircons are shown (Krogh, 1993) to have the isotopic properties (Sm/Nd) of the pan-African basement of the Chicxulub crater. In all the mentioned localities the two layers are in contact with each other, without an intervening layer. Not even a single layer of one fall season of leaves or plant material occurs between the two layers. If the upper, iridium-rich, layer is from another impact than the Chicxulub impact, they have to be simultaneous, and have to occur on the same pan-African basement - in itself highly unlikely, but not impossible. A 300Ka separation between the two layers in all the localities, as Keller posits for the separation between the Chicxulub impact and the iridium producing impact, is therefore excluded - barring a miracle."

Dutch radio interview

[Trestran]

For the Dutch slashdotters; Jan Smit said something about it on the Dutch radio(it's about 10 minutes into the stream), where he basicly called everything said by Kellar bullocks("a lott of mud throwing" and "facts that are verifiably wrong").

He has one of the samples of this study was based on (and (acording to above mentioned radioshow) the who divided up the original). In the end of the radiointerview he sugests letting all the original drill samples be tested by a third party for magnesium or calcium to prove if what Kellar has found are actual organism or just cristaline structures (as Smit seem to think). Sounds good to me, but then IANAPaleontologist.