Report Questions Role of Mexican Crater (In Dinosaur Extinction)

[Khephra]

By Associated Press

March 1, 2004, 5:05 PM EST


WASHINGTON -- A Mexican crater often cited as evidence that a single asteroid wiped out the dinosaurs may not have been involved in that extinction at all, according to a new report.

A group of researchers led by Gerta Keller of Princeton University contends that the impact that caused the crater occurred 300,000 years before the extinction.

In a paper appearing in this week's online edition of Proceedings of the National Academy of Sciences, the group cites a layer of sediment it found between the impact layer and the co-called K-T boundary that marked the mass extinction 65 million years ago.

Because it would have taken hundreds of thousands of years for the limestone layer to form, they argue the impact must have occurred well before the extinction.

more..........................................

http://www.newsday.com/news/politics/wire/sns-ap-crater-extinction,0,4282266.story?coll=sns-ap-politics-headlines

[RobertSeattle]

1. Damn, back to Theory "B"

[mccormack98]

2. Deccan Trap flood lavas of western India erupted 65 mya ...

While it is debatable whether a meteor hit the earth and caused the Dinosaur extinction, it is NOT debatable whether half of India erupted in massive flood lavas 65 million years ago. Over 500,000 sq kilometers of India erupted precisely at the time of the mass extinctions. The lavas flooded horizontally across the country side and did not form volcanoes. Some consider this event to be the cause of demise of the dinosaurs ...

[aquart]

3. Either one would cause massive immediate habitat change.

[Cessna Invesco Palin]

4. eeeeenteresting

I still don't buy the argument for the deccan traps being the cause (or at least the sole cause.) The eruptions happened over such a long period of time that it allows you to bring in all sorts of other phenomenon. That may be the *real* solution, however the deccan traps alone just don't seem like enough to cause massive worldwide extinction.

I'm also a bit wary of this study. The new trick of the anti-impact crowd, now that a pure volcanic solution is more or less demonstrably impossible, is to manipulate the K-T boundary position relative to the layer that derives from the impact. Furthermore, the accelerated climate changes, etc could massively affect the buildup time for carbonate rock, and they don't seem to be taking that into account at all.

Interesting work, though, and a fun read. Could use some more corroboration.

[Nihil]

5. Questionable evidence for "new" hypothesis

> However, Richard D. Norris of the Scripps Institution of
> Oceanography, responded that the group has incorrectly located the
> K-T boundary and noted it suggests the sediments were deposited
> mainly in deep, quiet water.
>
> "The laminations, particularly since they are not of uniform
> thickness or horizontal, could easily be the product of high energy
> bottom currents," he said.
>
> "The evidence they present, can in most cases be argued either way
> and so does not really resolve anything," Norris commented.

In other words, "oh, really?". Let's see how it pans out.

(Personally, I think it was the combination of the impact and the
Deccan Traps that stuffed the dinosaurs - this would ensure that
severe effects were felt across the entire landmass.)

Nihil