Just to straighten this out for you all:
> From: sterling
> To: epgrondine at hotmail.com;
> Subject: Re: [meteorite-list] The COMET that killed the dinosaurs
> Date: Fri, 22 May 2009 17:30:14 -0500
>
> Dear Doug, EP, List,
>
> >Keller, who as a matter of fact does believe a shower
> >was likely involved and allows that it could have been
> >cometary and happened over a longer span of time...
> Doug, while touting a series of impacts as the cause of the K-T extinction for a few years,
Keller now rejects any role for any impact, no matter how big... Well, sometimes she does... and sometimes not.
> The latest version of Kellerism presents the "view of the
K-T mass extinction mechanism where extraterrestrial
impact had no influence on the faunal mass extinction,”
http://www.dailyprincetonian.com/2009/05/06/23652/
>Keller has supported the volcanic theory since 2003:
http://www.sciencedaily.com/releases/20 ... 065930.htm
>She continues to do so today:
"The impact had little immediate effect on the planet’s biome.
Says Keller: “It didn’t kill the dinosaurs. In fact, it didn’t cause much damage that we can determine from the geological record [The Scientist]. “We found not a single species went extinct as a result of the Chicxulub impact,” says Keller."
http://blogs.discovermagazine.com/80bea ... xtinction/
>Not a single species. Didn't cause much damage. Check.
>While supporting, in some venues, the volcanic gas theory as the sole cause, she has also said "It was, instead, a progressive multi-event catastrophe, a concerted assault on the whole edifice of life by a combination of massive volcanism, multiple
impacts and their associated climatic and environmental changes."
http://www.geolsoc.org.uk/gsl/site/GSL/ ... /chicxulub
> [I don't know how she explains that, in the sedimentary layers between Deccan Trap basalt flows, there are dinosaur fossils. So, the Traps couldn't even kill the dinos that lived right on the same continent with them. OK. Back to Gerta's Story...]
> You will note that in this statement, she assigns impact an importance second only to the massive volcanism of the Deccan Traps, in her more recent statement she flatly asserts that impacts like Chicxulub don't "cause much damage." Elsewhere she has asserted that big impacts simply have no measurable effect on the Earth.
> But then, in 2006, she suggested that global warming weakened many species and that they were then extincted by another, bigger and yet undiscovered impact! "What the microfossils are saying is that Chicxulub probably aided the demise of the dinosaurs, but so did Deccan trap volcanism's greenhouse warming effect
and finally a second huge impact that finished them off."
http://www.geosociety.org/news/pr/06-47.htm
> If I had a hammer...
> For those who bother to read these posts because they're interested in impacts, this must be confusing. Shall we bottom-line it?
>Let's do that.
> The debate is about ~20 inches of strata, gritty limey stuff that is found between the level of the impact and the time of the extinction in sites near to Chicxulub (Mexico, Texas). It's about whether 1.) that 20 inches is dead pulverized debris from the impact slammed across the landscape and/or deposited by one of the biggest tidal waves in the history of the planet OR whether 2.) it's quiet sediment with traces of undisturbed lifeforms in it.
> Almost everyone who studied it says it's #1. Keller says #2. The answer depends on close examination of the material, something both sides have done (for decades). The evidence of life or no life is forams or no forams.
> What's a foram?
> Foraminifera are microscopic marine creatures with tiny stony skeletons (just like us, only forams wear theirs on the outside). When they die, the stone shell remains. It can persist for millions or hundreds of millions of years. Some limestones are virtually made out of foram skeletons.
> So the tiny crystals in this limestone layer are either forams or they're just crystals, once-living or never-living. And inorganic crystals are hard to distinguish from organic ones except in exceptional close and precise examination, SEM, Xray, and the like. I suggested everybody look at the evidence in:
http://www.falw.vu/~smit/csdp/debates.htm
(not because I favor Smit but because his pictures of Keller's samples are bigger and clearer than on the GeoSociety website).
> What I see (and I mean that to emphasize my subjectivity) is that a lot of Keller's forams are NOT forams. For example, their "cell walls" do not have the pores of a living cell, while "real" forams do. And likewise, some of Keller's forams ARE forams.
> The problem of whether this means anything is this: even if Keller's forams were true once-living forams, it would not prove that they were alive when they were deposited in this strata, since foram skeletons persist for a very long time. The "real" forams in Keller samples could have been dead for a million years before they got there or they could have died in place and in peace.
> No way to tell.
> There are other baffles. Are the few burrows really burrows? Has life worked this strata over (bioturbulence) or not? Even that is not decisive. If this is impact debris, would not the few surviving living things be scrounging through it in sheer desperation in the weeks or months after the impact before they starved or were poisoned by the disrupted environment? When many creatures die, the eating is good... for a while.
> No way to tell.
> That it's a tense issue is because for Keller to be right, dozens of scientists in the same field have to be wrong. Not just wrong -- incompetent. And the only way to explain Keller being wrong is the same reason: she's incompetent. You can see why folks would get a little snippy in this lofty debate of noble science.
> Another point is this. The strata under discussion are all found close to the impact site (Mexico, Texas). In Spain, in China, in Africa, there is NO separation of impact layer and extinction layer. They lay on each other as flat as a strap with no intervening strata.
> Now, IF there was a 300,000 year gap between the impact and the extinction, wouldn't it show up EVERYWHERE in the world? Or, at a minimum, wouldn't show up SOMEWHERE else? And, the truth is -- it doesn't. Not anywhere. Not even in undisturbed ocean sediment. (See: MacLeod, K.G., Whitney, D.L., Huber, B.T.,
> Koeberl, C., 2007. Impact and extinction in remarkably complete K/T boundary sections from Demerara Rise, tropical western North Atlantic. Geol. Soc. Amer. Bull. 119 (1), 101–115.) They were unable to find the stony corpse of even one Cretaceous micro-organism above the impact layer in any core sample.
> Not one.
> Here's a summary of those results:
http://gsa.confex.com/gsa/2004AM/finalp ... _80313.htm
> And here's the full paper:
http://www.univie.ac.at/geochemistry/ko ... AB2007.pdf
> One impact. One extinction. Simultaneous (well, geologically anyway). Adieu, T. Rex.
> That's what the evidence seems to say. Well, that's what it says to 97% of all the researchers in the field. Or maybe it's 99%. People who don't like the idea of impact as a process like Keller; she plays to them. But then, those people don't study impacts. Nasty things. And they don't know much about them. Then, she turns around and suggests even bigger impacts.
> She gets a great deal of press but very few supporters. She's very popular among people with a "cultural" interest in science.
> Now me, I take the long view. Once there were dinosaurs. Now there are not. They all died out at about the same time, along with the wonderful ammonites. (Who weeps for the ammonites? You dinochauvinistes!) It doesn't exonerate the Killer Asteroid if it took a thousand years, 100,000 years, or a million years to kill the Dinos. Still guilty as charged.
> Did they die all once? Gasp, Flop? Did it take 5000 years? 10,000 years? (There seems to be a Dead Zone about that length.) 25,000 years (which is all that remains of Keller's 300,000 years)? And even Smit says it took 35,000 years...
> So, how many years are we arguing about? Any?
> What difference?
> No dinos. Cryptozoologists see dinos in African lakes but it's a sad drab world -- there are no dinos in the lake, or on the plateau mountain of Auyan Tepui, and Conan-Doyle's dream of a Lost World is just a dream. No dinos, just a 3212-foot-high waterfall, the highest in the world. No pterodactyls in Illinois, although one was spotted in 1948. No plesiosaurs in Loch Ness. 'Tho I canna be sure... No living fossils except a deep-water fish and deep-water nautilii that kept their heads down (or shells down).
> They're gone. It was quick but probably not painless. Read more (much more) at:
http://books.google.com/books?id=ZaIO8wl_OZIC
if you can stand to read a GoogleBook, or this one:
http://books.google.com/books?id=kAup0TOL09gC
particularly Graham Ryder's article starting on page 31.
>He points out that the K-T boundary was quickly recognized almost two centuries ago. It was quite different than other boundaries and it was always clear that it was a sharp and abrupt change; Darwin called it "wonderfully sudden."
> Actually finding the boundary in the field was easy, even
in 1850 -- chalk overlaid with gooey clay. Thus, it is a
particularly ironic reversal that some geologists spend a
lot of time and effort to make it seem gradual when the
one thing geologists knew about it for centuries was
that it was abrupt.
> EP, you asked me to calculate the impact. It's been done by far better than I; I'll send you a list of URL's Off-List. Size?
> Think Big. Then... Think Bigger.
> At 170 kilometers, Chicxulub is the third biggest impact crater surviving on the Earth's surface, being exceeded only by the 250km Sudbury (1.85 billion years old) with twice its area and the 300km Vredefort (2.2 billion years old) with three times its area. They're arguing about whether there's an outer ring wall at 300 kilometers
> at Chicxulub (making it as big as Vredefort, unless Vreddy had an outer ring at 550 km...)
>
> Think of the movie "Armageddon" without the happy ending. The Chicxulub Fall wasn't a once-in-a-100,000,000-year accident.
> It was a once-in-a-billion-year accident. Did it briefly set the entire planet on fire? They say so... Take a good look at:
http://www.lpi.usra.edu/science/kring/e ... fires.html
> It changed the World forever. "50% of all genera were extinct. 17% of all animal families were wiped out. 50% of all angiosperms in North America alone went extinct. All of the dinosaurs save the birds were extinct. The great marine reptiles were gone. The pterosaurs were toast. The majority of the archosaurs and most diapsid megafauna was swept away. The archosaur grip on the ecologies that had lasted for 150 million years, was ended."
http://thedragonstales.blogspot.com/200 ... -fell.html
> And see, he didn't even mention the ammonites either....
> The same Joanne Bourgeois that thinks chevrons are not
tidal-wave-deposited (recently discussed on the List) is the one who modeled the tsunami from Chicxulub as being
4000 to 5000 meters high. A tidal wave three miles high. Hmmm.
> At the Brazos coast in Texas where Keller's sediments are, it was still 100+ meters. Bourgeois describes the sediments as full of fragments and shards: fish teeth, dead wood, shell fragments, chunks of smashed clay...
http://books.google.com/books?id=o-837r ... t&resnum=5
> Doesn't sound like quiet sedimentation to me...
> Unless, like Keller, you think the biggest impact in a billion years had no effect whatsoever -- none. "Not a single species went extinct as a result of the Chicxulub impact," she says.
> Lady, I have a bridge in Brooklyn I want to sell you... at a very reasonable price. Used, yes... but in excellent condition.
> Sterling K. Webb
EP - And I have about 1 federal employee at NSF who needs to be relieved.
> From: "Mexicodoug"
> Subject: Re: [meteorite-list] The COMET that killed the dinosaurs
>Hi Ed,
> The case we are discussing is the suspected and curious Nickel and Gold rich pseudometeorite or meteorite from DSDP Hole 576 recovered by UCLA's Cosmochemist Frank T. Kyte.
> Without giving my personal opinion, here are Kyte's thought on whether his object and the Chicxulub impactor in general is a COMET:
> "Analyses of a small fossil meteorite [sic] as well as the isotopic composition of Cr in K-T boundary sediments, point to a projectile similar to CARBONACEOUS CHONDRITE. Physical debris (i.e., Ni-rich spinels) in the global fallout is restricted to a single layer, and
there is no strong evidence to support any hypothesis other than a single, geologically instantaneous accretionary event. This observation, in addition to the apparent lack of an increased flux of 3-He at the K-T boundary are strong arguments against a comet shower
at 65 Ma. That the K-T meteorite [sic] is more similar to anhydrous, porous IDPs is also reason to suspect an asteroidal, rather than a cometary source for the K-T projectile."
Ref: Catastrophic Events and Mass Extinctions, eds. Christian Koeberl, Kenneth G. MacLeod: GSA Special Paper 356 Kyte, F.T., (2002) Boulder, Co., "Traces of the extraterrestrial component in sediments and inferences for Earth's accretion history", pp. 21-38.
EP- It comes down to 3He in comets, in some peoples opinions, In my own, given the gross evidence of carbonaceous chondrite, the 3 HE argument does not hold.
But in any case, given Raup and Seposkis chart of extinction periodicity, Weiler and Morrison either wasted tens of millions of dollars looking for Nemesis in the wrong place, as their hazard estimates show 1 per 100 million years, or they were looking for the wrong damn thing: asteroids instead of comets.
E.P. Grondine
Man and Impact in the Americas
