Re: [seymouria] Re: Article on Late Permian Biostratigraphy
- Thanks, Tom. I agree; John's time machine would definitely come in handy. Life forms in some of the inland seas may have died out even before they dried up. Emissions of methane and other poisonous gases could have occurred when rips appeared in the bottoms.Neal
From: fadingshadows2000 <fadingshadows40@...>
Sent: Wednesday, February 27, 2013 10:13 AM
Subject: [seymouria] Re: Article on Late Permian Biostratigraphy
That's a nice write up, Neal. Scientists will continue arguing over the exact cause of the event, but I believe something extraordinary occurred to start the process, then several factors followed. I don't rule out an extraterrestrial impact such as comet or astroid starting the whole she-bang, as they are likely suspects. But volcanos, poisonous gasses, weather, climate, and other causes continued the process. Pangaea could well have added to the process, but continental drift is slow, and animals tend to migrate to food and water. Unless there is none anywhere. Gasses would have poisoned the air, eventually killing almost all life. This is such an interesting subject, and I wish we had all the answers, but it's a complicated matter. Hey, we need John's time machine!
--- In email@example.com, Neal Robbins wrote:
> Â Â This is the link to the abstract of an article by Shu-zhong Shen et al. It was published in 2011. The title is Calibrating the End-Permian Mass Extinction. The authors state that the extinction event took place over a very long interval. This indicates that volcanism or an extraterrestrial object would not have been the main causal factor.
> Â Â Neal
> From: "uwtd@..."
> To: firstname.lastname@example.org
> Sent: Wednesday, February 27, 2013 7:36 AM
> Subject: [seymouria] Re: Article on Late Permian Biostratigraphy
> There evidence for an asteroid impact at the end of the Permian is equivocal at best. Benton favored vulcanism but I think it was symptomatic of the problem, not the worst of it. (Benton himself noted, in his WHEN LIFE NEARLY DIED, that vulcanism was even more massive at other times but there was no mass extinction at those times; note also the authors below say there's no clear correlation between extinction and an "igneous province"). The most important factor IMO was the formation of the supercontinent Pangaea at the end of the Permian. Once all the land was united and the seas between land masses eliminated the result was a much more arid climate, especially in inland areas. Dry weather caused plants to die, herbivore populations to crash and mass erosion to occur (fewer roots to hold soil). Some years ago, a paper note evidence for stepped, not catastrophic extinction.
> Btw Benton noted evidence for a release of deep sea methane--I suggest it was caused by methane being squeezed out of ocean deposits when the continents came together.
> --- In email@example.com, Tom Johnson wrote:
> > Although we know there were volcanic eruptions during that period, I think
> > there is sufficient evidence of more than one culprit in the cause of the
> > Permian extinction; one disaster led to several others, eventually bringing
> > about the massive extinction. The whole event may have been initiated by an
> > astroid/comet striking the earth, but other factors quickly added to the
> > destruction. We may never know, or truly understand the total event. That
> > it was a massive extinction, there is no doubt.
> > Tom
> > On Mon, Feb 25, 2013 at 8:23 AM, Neal Robbins wrote:
> > > **
> > >
> > >
> > >
> > > You're welcome, Tom. The authors have brought up an important issue.
> > > Although it has been thought that volcanic eruptions were the culprits in
> > > the end Permian mass extinction, the biostratigraphic evidence indicates
> > > that they may have not been the main causal factors.
> > >> >
> > > **> > says:
> > >
> > > Therapsid and other tetrapod fauna from the South African Karoo Supergroup
> > > provided the most detailed and best studied terrestrial vertebrate record
> > > of the Middle and Late Permian. The resulting biostratigraphic scheme has
> > > global applicability. Establishing a temporal framework for these faunas
> > > has proven difficult: magnetostratigraphy has been hampered by a Jurassic
> > > overprint, and intercorrelation with Permian marine sequences has been
> > > equivocal. Here we report U-Pb zircon isotope dilution thermal ionization
> > > mass spectrometry (ID-TIMS) dates for five volcanic ashes interbedded with
> > > fossils from the Pristerognathus, Tropidostoma, and Cistecephalus
> > > vertebrate biozones of the Beaufort Group. This temporal framework allows
> > > correlation to marine zonations and improves understanding of rates of
> > > faunal evolution and patterns of basin evolution. Our results identify no
> > > correlative vertebrate extinctions in the Karoo Supergroup to the marine
> > > end-Guadalupian mass extinction and raise the question of whether there is
> > > any record of a terrestrial extinction related to the Emerishan large
> > > igneous province.
> > >
> > > Neal Robbins
> > >
> > >
> > >
> > >
> > >
> > >