|Yes....... I have a thought......
Let's just say I have never, ever bought into the idea of an impact event being the ultimate, one and only, solo cause for the extinction of the non-avian dinosaurs. Having a degree in Physics, it's all fine and dandy I suppose for me to see the theorized effects that such impact(s) should cause..... both at initial impact and later on globally. (I did papers in some physics classes on the Jupiter Impacts and also on impact events on earth.) But the problem is that no one had ever done a massive comprehensive study of what effects actually took place via thoroughly looking at a good chunk of the preserved time interval before and after the impact event (at least not to my knowledge). I've read of sketchy reports before, like the articles by Archibald and Benton in "Encyclopedia of Dinosaurs", that hint at the theorized effects not being as severe as postulated after one actually takes a look at the preserved extinction record. The article in June 2002's "Di! sc! ! over Magazine" only puts the icing on the cake for me.... Fragile animals that by all accounts should have died out because of the massive climatic effects that should have taken place via the poisoning of the air and water (just like they die out today via industrial pollution).... didn't die out like they should have. The ones that did go bye byes were the ones that should have survived such an environmental holocaust.
What's even more telling is that the extinction event was supposed to have been much more severe in the Northern Hemisphere, particularly in North America itself, since the impactor hit at a 30 degree angle, pointing directly at North America. The resulting blast energy, instead of being directed straight into the earth (as we see at Meteor Crater in Arizona), was deflected right into the atmosphere..... with the resulting blast wave racing to the north across North America... making a b-line straight to Montana where Horner is conducting his study.
Too bad for the impactor lovers..... The blast wave apparently didn't make it to Montana.
What does this say about the rest of the globe?...... If North America wasn't hit as hard as it is theorized...... And it has been thought that the extinction rates on the rest of the earth were much less severe..... Well, you get the idea...
Now, the environmental perturbations caused after the initial impact, as dictated by numerous models and such, would have been world wide........ Nothing was safe...... Well, except for the salamanders, birds, and such, in Montana...... Once again..... I tend to think you get the idea.
Since I know that the majority have Paul's DA, I'll just refer you to his remarks on the KT extinction, that begin on page 293.... His writings basically sums it all up for me.
I will go so far as to say that with this new study out in Science entitled "Ascent of Dinosaurs Linked to an iridium anomaly at the Triassic-Jurassic boundary" that deals with finally finding an iridium anomaly (all be it a tiny one) at the Triassic/Jurassic boundary, and the apparent take-over by the dinosaurs after it, there might indeed be a connection with massive impacts and SOME recorded extinction events.....
March 2002's "Scientific American" had an article about extraterrestrial collisions and extinction events entitled "Repeated Blows". This article is a good one since it contains a nifty little chart called "Impacts, Eruptions, and Major Mass Extinctions" (I like pictures). This chart shows where in time the major documented mass extinctions had taken place, while also plotting when in time massive volcanics are known to have occurred, along with when known impact events had taken place and their associated crater diameters. When I look at the chart, what I see for the Permian's Great Dying are the raging Siberian Traps spouting out nasties for a good deal of time before 2 coinciding impact craters (Confirmation on the largest one is still pending ). For the Triassic/Jurassic we have the Central Atlantic Volcanos and a single impact close to the extinction. For the Mid-Jurassic we have massive volcanics and 2 impacts. For the Jurassic/Cretaceous we have big time volcanics! a! ! nd a few impacts all after, but close to, the boundary. For the KT, we have the mighty Deccan Traps raging for some time, a few impacts close to the boundary, and then finally Chicxulub.
To me, this equals malicious environmental effects caused by a volcanic onslaught stressing life before the impact(s) did its dirty work.
Did the impacts actually cause the volcanics? Highly doubtful.... It's true that there would have been massive shockwaves and such that would have had the potential to fire up volcanoes around the globe. But since the mentioned massive calderas and super volcanos were going on before and during and after the blamed impact events, it stands to reason that the impacts didn't cause the volcanics.... The impacts could have increased or even stopped their outputs... but they didn't cause them. I know of no impact event on earth as relatively massive as the one that formed the 1,300 km Caloris Basin on Mercury. This impact was so huge that is defaced the other side of the planet, directly inline with the impact site.... Such a scenario was once implide to the Deccan Traps and Chicxulub.
I'll say one more thing about the chart..... Though I am quite certain that we are dealing with preservational issues (being that more impact craters and volcanics are known from the "younger" rock record - Mesozoic through Quaternary).... as you approach the Trassic/Jurassic boundary, the Jurassic/Cretaceous boundary, and as you get closer to the KT boundary.... there is an apparent marked increase in impact events. The Tertiary, though, is completely littered with impact and volcanic events. I know very little about Tertiary extinctions. As I said, this marked increase could be nothing... Or, it could be something.
A thing I should also mention.... as does Paul in DA.... is that all through the chart there are single impact events and multiple impact events that have NO associated mass extinctions. Those that do have a documented mass extinction, do have the size thing going for them...... Craters 90 to more then 200 kilometers in diameter, and are associated with massive volcanics. The volcanics themselves on the other hands, ALL coincide with either mass extinctions or known faunal and floral shifts documented in the fossil record. Factor in continental drifts and inland sea transgressions and regressions, and you get a canvas who's paints paint a picture that doesn't say impacts are the most important villains when it comes to mass extinctions. They are only one in a multitude of players that can conspire together in the wrong place at the wrong time to wipe out entire ecosystems and their associated dominant fauna and flora. For the KT situation, the impact! (s! ! ) might just have been the last straw that broke the tyrannosaur's back.
Impacts obviously happen.......They just are not as severe as our mathematical models say they should be (Go figure.... Our math could be wrong!!!).
So....... I'm thinking that the environmental changes at the Triassic/Jurassic boundary before the impactor(s) were probably little, or were those not effecting the dinosaurs, or were simply very nonexistent. As far as I know, we don't have a firm understanding of the weather patterns during this time which would have dictated the environmental effects caused be the volcanics and the impact(s). This means that the dinosaurs were not under stress before the impact. Thus, being as resilient a life-form they definitely appear to have been (and "still are" I should also say), they were able to walk right into the Jurassic (literally as according to the Science article) pretty much unscaved by the "disaster".
The KT was a completely different story, as is being told by Horner's study. The dinosaur populations (at least in Montana) were having to deal with the environmental shockwaves being left behind and in front of the inland sea as it transgressed and regressed across the North American continent. Was this same type of scenario being played out on other dinosaur populations on other parts of the globe? I have no idea.... though it's highly plausible. Remember, your large bodies of water, like your seas, great lakes, and oceans..... dictate not only regional weather, but the obvious global climatic balance when it comes to ocean currents and the like. Making and/or removing such large bodies of water as inland seas woudl have disrupted with balance. And from what I understand, North America is the only place where good multi-million year old chunks of life, before the KT and after the KT, are preserved directly atop one another..... How does one take the extinction record p! re! ! served at only a few, little sites... all found in the same general area of the globe.... and apply the observations to the entire globe????? I mean, I have always read of KT studies only from locations in the USA. This biased sampling has never sat very well with me.
But anyway.... as I was saying..... The KT dinosaurs were being heavily stressed because of habitat shifts, faunal and floral die outs (as indicated in Horner's ongoing study), volcanics, and who knows what else.... and in flies Mr. Asteroid to deliver the final slap in the face.... not a full palmed, knockout slap mind you.... but one of those Bugs Bunny "take your glove off and smack them with it" slaps. As we have seen with a recent Nature article entitled "No 'Darkness at Noon' To Do in the Dinosaurs?" the dust cloud might now have been less of a problem then was once thought.... Not months of darkness....... How about a regular day in Seattle, Washington. As the article states, "... if dust really can trigger major extinctions, there should have been many impact-triggered extinctions in the past few hundred million years, because there have been many impactors larger than the few-kilometer minimum for a global dust cloud." The article goes on to blame global w! il! ! d fires and their resulting sun-blocking smoke clouds as the main culprit for the dinosaurs' demise. Only an impactor 10 kilometers and larger in diameter could throw up as much vapor that would be needed to cause these global fires. The problem is that even this doesn't fit the data we have in our hands..... especially according to the aforementioned chart.
And this still does not explain why salamanders, birds, and other fragile animals in Montana, apparently went about their business as usual, while the non-avian dinosaurs lost their battle for survival. As I hinted before about weather.... How those high level winds were blowing and what weather patterns were in effect around the globe, and even the very seasons in place at the time of the impact, would have dictated the dissemination of the impact and volcanic effects around the globe..... Some regions would have been hit hard, others effected just a bit...... while still other areas of the globe being completely unaffected.
All I can say is that I'm glad Horner is doing this study.
And one more thing...... Though the reported evidence thus far is sketchy at best and shouldn't be trusted just yet.......I have always said that I expect us to find Laszarus Dinosaurs..... I will be completely shocked if we don't.