Re: (fwd) Chicxulub didn't do it!

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

> But a few brave souls,

Courage is not automatically a desirable quality. Not every hero deserves
reverence.

> mainly paleontologists, doubt that Chicxulub was
> the sole culprit.  There actually may have been *multiple*, simultaneous
> impactors.

Yes.

> Then, there were those great volcanic outpouring about
> 65 million years ago that spread lava out over huge areas, now
> to be seen as the immense lava flows of India's Deccan Traps
> and the Siberian Traps.

Ts, ts... the Siberian traps date from around the P-Tr mass extinction (the
precise dating is still not certain, though). The Deccan traps represent
several episodes of outpouring... at least in one place, the K-T boundary is
in an intertrappean sediment, not in a lava layer. Is there a place where
the latter is the case?

> G. Keller, a Princeton paleontologist and authority on fossilized marine
> plankton called "foraminifera," is now a Chicxulub doubter.

Hasn't she always been?

> Keller's analysis of the Chicxulub drill core shows that
> foraminifera prospered for 300,000 years *after* the Chicxulub
> impactor made its huge crater and debris layers.

Does it show this? K sediments in the crater need not mean that the crater
was formed before the K-T boundary. To the contrary, it is expected that
lots of huge chunks of rock have fallen into the primary crater which had,
at the surface, more or less vertical walls and was... how much? 30 km deep?

> Of course, Keller's findings are challenged, but some of the
> challenges are perhaps suspect.

Yeah, perhaps. Put up or... :-)

> N. MacLeod, a paleontologist at London's Natural
> History Museum, remarks:
>
>    It's not about science...

Indeed I wonder why Keller _never_ mentions the age of the Chicxulub crater.
Which is 64.98 +- 0.05 Ma, according to the most precise method known (ratio
of uranium to lead in zircon crystals). Or does she, somewhere?

> [...] traps inundated Siberia, Africa, North America,
> and even Antarctica.

This "even" proves that the comment was written by someone with precious
little knowledge of geology.

> These lithic floods are chronologically tied to many of
> the extinctions in the fossil record.

I wouldn't say "many". Data from Rampino's lecture Catastrophic Geology (and
Rampino is a volcanologist):

Trap        Age (Ma ago)        Nearby mass extinction        Climate change

CRB (Columbia... forgot the rest)        16 +- 1        -----        cooling
Ethiopian        31 +- 1        -----        cooling
North Atlantic        59.6 +- 1        -----        warming
Deccan        65.8 +- 0.1 (weren't there more episodes before and after
that)?        K/T 65.0 +- 0.2        -----
Madagascar        87.6 +- 0.6        -----        warming
Rajmahal        116 +- 1        Apt/Alb 112 +- 1.1        -----
Serra Geral        132 +- 1        -----        -----
Karroo        183 +- 1        Middle Jurassic 183 +- 1.7
CAMP (Central Atlantic Magmatic Province)        201 +- 1        Tr/J: 199.6
+- 0.3

I don't know how accurate all those dates are; e. g. the Tr/J boundary is
now usually dated around 201 Ma ago and considered slightly older than the
CAMP basalts... but all in all the correlation between traps and mass
extinctions looks rather poor.

> This book is well-written and suitably politically incorrect.  Here's the
> "other side" of all those extinction events.

To be the next Galileo, it's not enough to be pursued by an orthodoxy. You
also have to be right.
-- Carl Sagan, hopefully not misquoted