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Posted on 05/19/2014 4:31:05 PM PDT by SunkenCiv
Here, for the first time (to our knowledge), we are able to demonstrate unambiguously that the impact at the Cretaceous–Paleogene boundary (K–Pg, ∼66 Mya) was followed by a so-called “impact winter.” This impact winter was the result of the injection of large amounts of dust and aerosols into the stratosphere and significantly reduced incoming solar radiation for decades. Therefore, this phase will have been a key contributory element in the extinctions of many biological clades, including the dinosaurs. The K–Pg boundary impact presents a unique event in Earth history because it caused global change at an unparalleled rate. This detailed portrayal of the environmental consequences of the K–Pg impact and aftermath aids in our understanding of truly rapid climate change.
Abstract: The mass extinction at the Cretaceous–Paleogene boundary, ∼66 Ma, is thought to be caused by the impact of an asteroid at Chicxulub, present-day Mexico. Although the precise mechanisms that led to this mass extinction remain enigmatic, most postulated scenarios involve a short-lived global cooling, a so-called “impact winter” phase. Here we document a major decline in sea surface temperature during the first months to decades following the impact event, using TEX86 paleothermometry of sediments from the Brazos River section, Texas. We interpret this cold spell to reflect, to our knowledge, the first direct evidence for the effects of the formation of dust and aerosols by the impact and their injection in the stratosphere, blocking incoming solar radiation. This impact winter was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis.
J.V., J.S.S.D. and H.B. designed research; J.V., J.S., and H.B. performed research; S.S. contributed new reagents/analytic tools; J.V. and J.S. analyzed data; and J.V., A.S., J.S., S.S., J.W.H.W., J.S.S.D., and H.B. wrote the paper.
(Excerpt) Read more at pnas.org ...
doi: 10.1073/pnas.1319253111
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1319253111/-/DCSupplemental.
This folks is how most scientific papers appear. Dreadfully boring, bounded by the limitations of the study, and presenting findings supported by the evidence with an informed interpretation of the results. Designed to put any insomniac into deep sleep.
Compare and contrast this with the political activist nonsense in the climate change world, or the soon to come rebuttal from the Institute for Creation Research.
This study only applies to sediments along the Braxos River, where the study team probably enjoyed some mighty fine barbeque during their off time. It can be compared with other studies from other sediments in other locations to help confirm or deny their findings. If rejected by the Geological community, it’s back to the drawing board and the tired old Suburban research wagon. If confirmed, we can advance our understanding of the ending eons of the Cretaceous.
Don’t expect the clueless science press to jump on this one way or the other.
To read later. This has long been thought to have been the cause of the mass extinction that killed the dinosaurs and it would be good to get more confirmation. Next up, did global warming cause or contribute to the Permian extinction. If it did, it would pose a counter to the AGW nonsense currently being pushed because there were catastrophic volcanic basalt flows and coal field burning in the geologic record that put to shame our puny efforts at increased CO2 plus, the CO2 was scrubbed out of the atmosphere once the lava floods that covered much of Siberia and the coal fires petered out.
There are also a couple of other mass extinctions it would be good to understand because the “science” of the left is pushing the idea that we are causing another, even worse extinction. Knowledge vs rhetoric is a good thing.
Ah, yes, the Chevy Chicxulub. One of the biggest SUVs in history.
It left the company in a hole when the gasoline price spiked.
The Permian-Triassic extinction was also caused by impact, but the candidate crater hasn’t been identified.
:’) And this is just the abstract, I’d have to be affiliated to get access to the full paper. Ain’t that America...
It was already too high since the dinosaurs had barely decomposed enough to burn then.
Yep, and that costs big bucks unless you are affiliated with a major research university. Since I departed from my academic affiliations some time ago, I have difficulty keeping up with the real scientific literature. I’m left to sort through the political activist drivel.
I read a book about the Permian extinction by geologist who didn't think the extinction was caused by an asteroid because there was no iridium layer associated with it. He believed the extinction was associated with the Siberian Traps and the release of enough magma to cover Western Europe over the course of one million years.
When I was an undergrad and graduate student, impacts were poo pooed by the crusty old curmudgeons that ran the show, and all that continental drift was clearly daft.
Scientific understanding advances like a glacier, quite slowly and the nonsense is eventually cast aside as some lateral moraine. So will be the remains of today’s climate change rantings in good time.
I know there is evidence of one but, to me, unless it caused the Siberian Traps, it was icing on the cake, so as to say. That was the largest extrusion of lava of which the geological records remain. There is also some thought that the Deccan Traps contributed to the K-Pg extinction.
Jan Smit is quite a mench. From T. Rex and the Crater of Doom:
...I found myself next to a tall blond man who introduced himself, in a pleasant Dutch accent, as Jan Smit, from Amsterdam. Jan said to me, "I read a story about your iridium in New Scientist, and I want to tell you that I've confirmed your discovery. I have a really complete KY boundary section at Caravaca, in Spain,and it has anomalous iridium too!"...Major hat tip, Jan Smit!It would be some time before I fully understood the degree of personal integrity that lay behind Jan's opening remark. Studying the rock record of southern Spain for his Ph.D. thesis, Jan had been intrigued by the abrupt KT extinction of forams at Caravaca, Just as I had at Gubbio. Looking for a chemical clue to the KT event, he contacted Belgian neutron activation analyst Jan Hertogen, just as we [Luis and Frank Alvarez] had contacted Frank Asaro at Berkeley. Hertogen had found high iridium values, but at the time Jan was sick with mononucleosis and not up to looking at the chemical data. As he was recovering, he came across the article about our work, looked for iridium in the data printouts, and there was the immediate confirmation.
Some scientists might have been tempted to claim an independent discovery or quickly rush out a paper to establish priority of publication. But from the moment we met, Jan treated his analysis as a confirmation of our discovery. This is the high standard of ethical behavior that scientists aspire to, and which makes scientific endeavor possible, but which is not always met because scientists are very human.
I had heard the Permian extinction was caused by continental drift. All the shallow seas where Paleozoic Era life flourished were closed, pushed up and drained. Or so I heard.
The Siberian Traps didn’t cause anything but a little local discomfort, same goes for the Deccan Traps. And in neither case was there a massive increase in local volcanic activity all at once. Volcanic eruptions are not even a boil on the ass of a boundary event impact.
There was and still is a very high resistance by the fossil academics to the impact extinction model. Iridium was anomalous because it is so rare on Earth, including in the junk barfed up by volcanoes, so that stood out to Walter Alvarez, whose father Luis Alvarez was a physicist and realized the significance of the find right away. *At one time* iridium wasn’t known from the PT boundary, now it is.
http://www.sciencedirect.com/science/article/pii/0031018293901286
The theories I have heard recently seem to focus on methane, although what the source of the methane was ranges from volcanism to methane hydrates to microbes. Many also think that the extinctions occurred in waves over a period of time, rather than one sudden event.
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