Cretaceous warm climategamoonbatMay 17 2007, 12:10:00 UTC
This is very good. There does seem to be a goof in the last sentence, though. You write "To say compare the age of the dinosaurs...." I think you just meant "To compare the age of the dinosaurs...."
I wonder if all of these arguments also apply to the comparison with the PETM?
Paleocene-Eocene Thermal MaximumgamoonbatMay 17 2007, 13:14:52 UTC
Right. How much different was the Earth System of the Tertiary from the Quaternary? When did the 100,000 year orbital forcing start to play such a prominent role?
Re: Paleocene-Eocene Thermal MaximumtheclimateblogMay 17 2007, 13:33:28 UTC
Good guess on my part! I'll have to do more research on this - I know the climate warmed really rapidly, and that it's believed to be due to methane clathrates (that's how I read about this in the first place- I was researching clathrates). I just might have to do a post about methane clathrates, considering they've got important implications for climate warming...
I found a nice image on Wikipedia (I don't allow my students to use it as an academic source, but there's a lot I like about it, especially its images):
Excellent points. Because I'm a structural geologist from western North America, though, I'm going to nit-pick a little on point #1 (in the interests of making your argument stronger!).
The physiography of western North America was different in the Cretaceous, but there were mountains there. In fact, some studies of metamorphic rocks in Nevada suggest that there were much higher mountains there in the Cretaceous than there are now. And the high topography further to the east (Colorado, for instance) probably got its start in the latest Cretaceous/early Tertiary (Laramide orogeny). So western North American mountains, at least, probably aren't to blame for the change in Cenozoic climate. (The Himalayas, on the other hand, and the splitting of the Gondwana continents, especially Antartica - yeah, those are more the right time.)
There are some good paleogeographic maps of western North America done by Ron Blakey at Northern Arizona University -- I think they summarize the big picture as tectonicists (and the oil company geologists, as
( ... )
Thank you! It's interesting, because paleoecologists and paleoclimatologists often throw around the idea of the Rocky and Sierra Nevada uplifts when they're talking about the biogeography and climate of North America - not being a geologist, this is the first I've heard that this area had mountains then! Usually people talk about it as though the mountains hadn't formed yet. I'm wondering if this is newish information, or if people just fill in the blanks (e.g., if the Sierra Nevadas and Rockies hand't formed, there must not have been anything there)? It was even a subject on my biogeography final exam (we were asked about grassland formation and Paleocene/Eocene cooling.
I'll edit my post accordingly. Thanks again for the geology lesson!
I don't think it's new-ish - now I wish that I had an old Historical Geology textbook or something so that I could give a definite source. But I think even pre-plate tectonics historical geology courses would have talked about the Sevier (+ Nevadan) and Laramide orogenies (= mountain-building events). And in the 80's, when I was an undergrad, we talked about Andean-style tectonics in the late Mesozoic. The big tectonic events in the Tertiary made western North America less like the modern-day Andes - the subducting plate off western North America disappeared, and left California bounded by the San Andreas Fault instead of a subduction zone; and Nevada collapsed and spread horizontally, giving us the Great Basin between the Sierras and the Rockies
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That's right - our humidity comes from maritime tropical (mT) air masses from the Gulf and Caribbean. Interestingly, though, I've read that the spikes in humidity associated with heat waves in the Midwest is possibly linked to corn farms, where corn adds moisture to the air through evapotranspiration.
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I wonder if all of these arguments also apply to the comparison with the PETM?
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I'm blanking on your PETM - all I can think of is Paleocene-Eocene Thermal Maximum? :)
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I found a nice image on Wikipedia (I don't allow my students to use it as an academic source, but there's a lot I like about it, especially its images):
( ... )
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The physiography of western North America was different in the Cretaceous, but there were mountains there. In fact, some studies of metamorphic rocks in Nevada suggest that there were much higher mountains there in the Cretaceous than there are now. And the high topography further to the east (Colorado, for instance) probably got its start in the latest Cretaceous/early Tertiary (Laramide orogeny). So western North American mountains, at least, probably aren't to blame for the change in Cenozoic climate. (The Himalayas, on the other hand, and the splitting of the Gondwana continents, especially Antartica - yeah, those are more the right time.)
There are some good paleogeographic maps of western North America done by Ron Blakey at Northern Arizona University -- I think they summarize the big picture as tectonicists (and the oil company geologists, as ( ... )
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I'll edit my post accordingly. Thanks again for the geology lesson!
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