Re: Hell Creek (long)

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Tommy Tyrberg" <tommy.tyrberg@norrkoping.mail.telia.com>
Sent: Saturday, June 01, 2002 11:21 PM

> It is very doubtful if even global wildfires could really cause "darkness
> at noon" for any length of time. The reason is that the smoke would stay
in
> the troposphere and be washed out quickly by rain. On the other hand many
> pyrochemicals are toxic, so very large scale fires would be very unhealthy
> even for animals that were not directly affected by the fire.

What's more, the following book says (without specifying) that "pyrotoxin"
susceptibility is often very different between closely related animals, so
this might (untestably, I assume) explain the selectivity of the extinction.

Louis de Bonis: Évolution et extinction dans le règne animal, Masson 1991

> As for the Deccan traps, [...] Lakagígar 1783 [...]
> killed 75% of all cattle on Iceland, mostly through fluorine poisoning and
> by stunted grass growth because of sulfur dioxide.

How much fluorine is there in the Deccan basalts? Is it possible that there
was much less than in Iceland's magma?

> Note that India was isolated out in the middle of the Indiam Ocean at the
> time of the reuptions, so the dinosaur couldn't have recolonized from
> elsewhere during quiet intervals.

Depends on how long the connection via Kerguelen held, and how far it really
was away from Madagascar and Africa. (Current majority consensus: India was
indeed isolated at the K-T.)

> Another aspect that I think hasn't been mentioned in this thread is that
> the Chixculub bolide impacted on partly dolomitic rock. This means that
> large amounts of sulphur were injected into the stratosphere.

Gigantic amounts of sulphur (dioxide) must indeed have been injected into at
least the stratosphere and have led to cooling sulphuric acid droplets and
then acid rain, but because of the anhydrite (waterless gypsum -- calcium
sulphate) at the impact site, not because of the dolomite (mixed
calcium/magnesium carbonate). :-) The latter yields carbon dioxide when
vaporized, though -- greenhouse effect and acid rain, too.

> This may have had a very significant effect on climate.

Indeed -- first very cold weather, then very hot weather. The latter is
(apparently) recorded in the worldwide 16O/18O ratio shift in marine K-T
sites.

> Also the Chixculub bolide hit in (admittedly shallow) salt water. This
> means that large amounts of water vapour and _salt_ must have gone into
the
> stratosphere. The salt may have been very significant since chlorine is
> very bad for the Ozone Layer.

Haven't thought of that... may not matter considering the nitric oxides :->
or may prolong their effect. Could probably be simulated.

> Another extinction mechanism that I don't think has been mentioned in this
> thread is the tremendous earthquake (about 12(!) on the Richter scale).

I've heard 11, 12.4 and between 10 and 12.8 recently. I don't think that
actually matters, though... :-) -- should literally knock down all big
standing animals.

> Furthermore very large amounts of methane would have been liberated
> from methane hydrates and gone into the atmosphere and reinforced the
> hothouse effect from carbon dioxide.

Sure.