[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Pollen From Permian/Triassic Extinction Show UV Induced Mutations



> > > There is no evidence for such a big impact at the end of the Permian,
> >
> > Not at the moment.

BTW, what has really become of the 3He inside the fullerenes?

>  Which certainly suggests other factors played a role in mass extinctions.

Absence of evidence is no evidence of absence.

> > > nor was the extinction very sudden.
> >
> > Constrained to 8,000 years or less by cyclostratigraphy (on the mountain
> > called Gartnerkofel in Austria, you can see the Milankovic cycles in the
> > sediment), according to Rampino.
>
> Up to 50,000 in the Karoo basin.

I don't know, but I bet that the resolution of those terrestrial sediments
is much coarser than that of marine sediments which are fine enough to
record Milankovic cycles.

> >Then why was there a fungal spike? (Globally!)
>
>  Earlier extinction on land.

OK. But then we need at least 2 causes for the P-Tr mass extinctions.

> > > Extinction on land in South Africa was apparently gradual.
> >
> > Could you be more precise? How was the Signor-Lipps effect and suchlike
> > excluded?
>
>  They mentioned a demise of smaller taxa before large ones e.g.
Pelanomodon.

This sounds like they didn't exclude the Signor-Lipps effect... smaller ones
are easier to overlook... And what could have killed off animals with small
adult size but not small juveniles of bigger species?

> > > Smith and Ward noted evidence for stepped extinction in South Africa
> > > associated with a drier climate, or a "sudden, possibly catastrophic
drought
> > > at the end of the Permian."
> >
> > Global synchronous aridity would be needed for that
> > -- and why should that happen?
>
>  Maybe regression reached a certain threshold where habitat
loss/fragmentation occurred.

But globally?

> The continents were still connected so many habitats could have turned
arid with regression, as they were far from the sea.

So what about Pangaea's long coast, and its long rivers?

> Btw, the evidence for catastrophic drought suggests UV isn't needed to
explain the mutations.

:-) But we can't rule out that the UV irradiation peaked at the same time.
And there's no evidence for catastrophic _global_ drought, is there?