Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: frethack on 22/05/2008 03:09:32
-
Ive been looking for this article for some time now. Finally found it after a quick email to a very helpful gentleman (I use the term "gentleman" loosely here [;D] ) spurred my thought processes. It appears that I was searching for the article before it had actually been published...imagine that.
Anyway, a group of scientists seem to be able to link the disappearance of Clovis man, the North American megafauna (horse, giant sloth, mastodon, short faced/cave bear, etc.), and the 1000+ years of cooling (Younger Dryas) that prolonged the end of the Wisconsin glaciation.
Well...here is the PDF for the journal article from Proceedings of the National Academy of Sciences. Its kind of a long and arduous read, so Ill include a popular science article too.
http://www.pnas.org/cgi/reprint/0706977104v1 (http://www.pnas.org/cgi/reprint/0706977104v1)
Hers a popular science article....there are quite a few of them, but Ill post one.
http://space.newscientist.com/article/dn11909-did-a-comet-wipe-out-prehistoric-americans.html (http://space.newscientist.com/article/dn11909-did-a-comet-wipe-out-prehistoric-americans.html)
Many thanks to the gentleman(?) for jogging my increasingly strained memory!
frethack
-
Ive been looking for this article for some time now. Finally found it after a quick email to a very helpful gentleman (I use the term "gentleman" loosely here [;D] ) spurred my thought processes.
Hers a popular science article....there are quite a few of them, but Ill post one.
http://space.newscientist.com/article/dn11909-did-a-comet-wipe-out-prehistoric-americans.html (http://space.newscientist.com/article/dn11909-did-a-comet-wipe-out-prehistoric-americans.html)
Many thanks to the gentleman(?) for jogging my increasingly strained memory!
Watch those who's kindness you question, DUDE!
-
Oh, there is no questioning your boundless kindness, JimBob :)
(This is probably the point where I should bow humbly before your cyber-boots)
-
Hob-nail boots, soldier.
-
ok, i have a moment to just screw off and educate myself a little more.
i have known about the meteor theory for a while and after refreshing my brain, i am not greatly convinced by the theory. the reason i say this is the from the end of the last previous glaciation (illinois-riss) to the end of the wisconsian-wurm, CO2 levels have fallen rather consistently, ending in a sudden rise at the end of the younger drias.
there are other just as plausible explanations, esp. Milankovitch Variations, which coincide rather well with glacial periods. other factors are also involved, including possibly solar sun spot cycles, the earth's polar precession and many other possible factors.
one of the biggest problems i have with the impact theory is the lack of evidence. it falls onto the ice sheet and gets eroded away.
so - who knows?
-
I would completely agree that this is not proof, but it is interesting evidence. According to the article, an actual impact would not have occurred, but something more akin to a Tunguska type event, except on a larger scale (*IF* Tunguska truly was a comet).
Black carbon mats, carbonaceous silts, and carbon rich clays in more than 50 sites across N. America, with some having Clovis artifacts directly below, but not above (in 10 of 10 previously well dated and studied Clovis sites). Carbon spherules, magnetic microspherules, microdiamonds, fullerenes with He3, and Ir many times above crustal abundance detected in most sites inside the mats, as well as 15 of 15 Carolina Bays that were sampled (they are explaining the majority of them as blowouts from the blast...I dunno about that one). The scientists claim that it all seems to radiate from the Great Lakes region (deposition thickness and abundance). The layer is at about 12,900 ybp, and they claim it coincides well with both the onset of the Younger Dryas as well as the Clovis and Megafaunal extinctions. I also wonder exactly how much fresh meltwater would be needed at one time to slow down the Gulf Stream enough to cause something like this. Again...evidence, but certainly not proof. Id love to see it explored further.
I am personally partial to some combination of solar, precessional, and Milankovich cyles in providing the forcing agent that takes us between glacial and interglacial periods, with some solar dominance, but, to my knowledge (which is limited), I dont know of a Younger Dryas type event occurring after any of the other known glaciations.
-
if i could see the remains of a family of mammoths in what is now Iowa, all of them being killed at the same time and all of them having burned tusks, teeth, toenails - stuff on the outside - i would feel much more comfortable.
-
Agreed. This one, lonely journal article doesnt constitute a "large body of evidence", and it seems that ET impacts get the blame for quite a few mass extinctions/drastic climate changes. They cant *all* be comets and meteors.
-
I always refer everything big to something else thats big. I was looking at some underwater maps of the ocean floor and an impact hit in Australia and exited at the Mediterranean Sea, pushing up and depositing Mt. Everest the highest place on Earth. Look up. There's the comet. Our moon. We can map its' weather because the environment causes the weather patterns to repeat themselves. Take a look at the Columbia River Gorge and scablands before you say no. The impact that caused the extinction of the dinosaurs also caused most of the weather cataclysms that we blame on other impacts.
I have to say that the only thing I could come up with, which might have caused all the glaciations that followed the great glacial melt off, were "mini-prehistoric environments" caused by the glacials themselves, and the large changes in land forms when the floods washed through... In any case, the deepest ravines on this earth are still filled with water from these mini-environments.
-
using big = big would mean that no flea could have spread bubonic plague. and there is now enough evidence to indicate that the Permian extinction, which took place over 300,000 years, was due to a drastic drop in atmospheric oxygen.
The above post has no factual basis, it is just speculation. for example, if you were aware of the detailed geology of the scab lands, you would know that the floods that formed them happened repeatedly - over 50,000 years. the events actually repeated themselves so often, varved sediments were produced by the repeated catastrophic flooding.
were my right arm not shattered i would answer all of he above assertions in detail. all i can do now is say that the understanding of geology that underpins the previous post is "limited."