[meteorite-list] P/T transition

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 18 Dec 2009 17:05:58 -0600
Message-ID: <469A2F10750C44A495EDF70BE4D16410_at_ATARIENGINE2>

Hi, EP, List,

The Indian Deccan Traps basalt-flood vulcanism
began before dinosaurs were extinct, continued
through the extinction event, and for a few million
years afterward.

The region of the vast lava flows has some major sites
of fossilized dinosaur eggs, not after the eruptions,
but during and in-between them, thus demonstrating
rather conclusively that several million years of the
Traps (the second biggest flood-basalt region on the
planet) did not kill off the dinosaurs, even the ones
that lived there, although no doubt they complained
that the neighborhood was going to... er, downhill.

The individual layers of the Traps have been well-dated;
the so-called crater has not been dated at all. I say so-
called crater because it is regarded with great skepticism
by many including me (who is as pro-impact as you'll
find hereabouts).

All they have done is look at the shape. I do not find
that shape convincing -- the "central peak" is not in
the center but over near the rim (impossible!) and the
rim walls don't look like rim walls to me.

They know they need actual evidence. I quote: "The
team hopes to go India later this year to examine rocks
drill[ed] from the center of the putative crater for...
shattered and melted target rocks,... breccias, shocked
quartz, and an iridium anomaly..."

But... but... how could it have circular walls (or half a
circular wall)? Well, 65.3 million years ago, India wasn't
IN India. India was a big island off southern Africa, just
east of Madagascar! (50 million years before that, it was
part of (or attached to) Antarctica. India was on a long,
slow sea voyage to the north.

So, about 30 million years ago, it smacked into Asia and
pushed the Himalayas up and lifted the low-lying Tibet
Plateau into the sky. Anyway, we don't know where the
exact plate boundaries of the cruising Indian Plate were
and don't know if the "crater" traveled north with it. Or,
it could simply be that the "crater" is nothing but some
wrinkled terrain that India pushed into and bent... hard.

We WON'T know without a lot of drilling and sampling
and dating over vast stretches of ocean and gravimetric
surveys and a buncha stuff that costs millions. Until then,
we have press releases which are cheap but might inspire
a little money...

I'm not contributing any of my few pennies, but I hope
somebody does. The crater could have come north with
India or it could have been in the way when India arrived
or it may date to 253 million years and be a piece of the
Permian crater plucked off Antarctica and drug off by the
Indian Plate or it could be nothing much at all.

It is worth noting that it was almost exactly on the other
side, 180 degrees, from Chicxulub at the time. It may be
what planetologists call "chaotic terrain" and which is
formed by the shock wave of an impact directly on the
other side of a planet. (There's an example of that on
Mercury, a suspected example on Mars, and so forth.)
It's more likely that the Traps flow of lave was unleashed
by the Chicxulub impact.

Of course, on a planet with Earth's apparently unique
tectonics, there's lots of chaotic terrain from all kinds of
causes.

As for what set off the Siberian Traps, my money's on
the as-yet-undiscovered (?) Great Permian Whacker.
I say "undiscovered" because someday we may have
enough geomagnetic and gravimeteric data on the
Wilkes Land crater in Antarctica to convince.


Sterling K. Webb
-------------------------------------------------------------------
----- Original Message -----
From: "E.P. Grondine" <epgrondine at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, December 18, 2009 12:16 PM
Subject: Re: [meteorite-list] P/T transition


> Hi Paul -
>
> One is still left with the question of what set off the Siberian Traps
> lava outflows. We now know that the Shiva impact amplified the Deccan
> Trap outflows.
>
> E.P. Grondine
> Man and Impact in the Americas
>
>
>
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Received on Fri 18 Dec 2009 06:05:58 PM PST