[meteorite-list] Libyan (looks like a) crater

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 9 Dec 2009 14:47:49 -0600
Message-ID: <47A5C42784D44DC586E970F4FE61F3D6_at_ATARIENGINE2>

Hi, Randy, List,

Two thumbs down on this WWII crater. Here's
some why's:

http://glenavalon.com/ldglass.html
    "The distribution is approximately elliptical,
~130 km by ~50 km with the major axis ~NNW
by SSE... The [present] dune sand and dunes
have been formed in a time estimated to be less
than 1,000,000 years, yet the fission track dates
of the glass have a mean of ~28,000,000 years...
[The] chemistry [of] the glass cannot have been
fused from the local exposed sandstone... "

A map of the Great Sand Sea with the LDG
area indicated can be found at:
http://www.pisces-press.com/C-Nav/images/ldg-area.jpg

LDG covers about 5000 km^2 in Egypt, not
Libya. The present surface is deeply overlayed
on the surface of 28 mya. At that time, the
surface was shallowly underwater throughout
most of the area of the Fayyum Depression.
Underlying the present surface is ~300 meters
of limestone formed in those shallow waters.
And underlying that is more sandstone.

It's hard to estimate the total mass of LDG
produced. Present day finds are not in situ. Some
LDG shows evidence of aqueous transport and
long aeolian weathering. Some LDG has been
found weathering out of the limestone outcrops.
Considering that any LDG is still found, the
total mass may have been in the millions of tons.
The surface distribution is estimated at 1500 tons.

Clayton (the discoverer of LDG) and Spencer
said that 10% of their finds were worked human
artifacts, from the Alteran peoples, 30,000 to
18,000 years ago. Isolated LDG pieces have
been found up 140 miles from the strewnfield
in conditions suggesting human transport

The 2006 discovery of "Kebira" crater, far to the
SW, has been suggested as a source for LDG. Here's
a report by someone who visited it and doesn't think
it's a crater:
http://www.pisces-press.com/C-Nav/crater.htm

An excellent history and summary of speculation:
http://www.saudiaramcoworld.com/issue/197905/desert.glass-an.enigma.htm

Another summary:
http://www.pisces-press.com/C-Nav/ldg.htm

Mark Boslough of Sandia thinks he has the
answer, but the expedition he was with doesn't
think it's a crater:
http://www.sandia.gov/news/publications/technology/2006/0804/glass.html

At least one case has been made for the non-
impact origin of LDG (nice pictures):
http://www.b14643.de/Sahara/LDG/index.htm



Sterling K. Webb
-------------------------------------------------------------------
----- Original Message -----
From: "Randy Korotev" <korotev at wustl.edu>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, December 09, 2009 9:21 AM
Subject: [meteorite-list] Libyan (looks like a) crater


Dear List:

I received this intriguing e-mail today from someone I don't know.

=========================

Dear Randy, I am a geophysicist and had a recent
trip on Libyan desert for campaign of geophysical
investigations, mostly GPR and Geoelectric
tomography. Going back to the camp I found at
sunset -due to low angle light- something strange on the flat desert
surface.

I found a perfect circular crater with melt sand
scattered around . sand grains are melt and
embedding larger quartz grains. In my opinion
that's a impact crater and sand is melt because
of the heat wave. Larger grains had no time to melt .

That melt rock has a black matrix-nothing like
that in the area, also there are no similar
structures in that flat, flat flat desrt
surface, sand is only silica and quartz grain and
no dark matrix can be seen for kilometers.

I made a few geophysics on the spot and found big
electric anomalies and very anomalous readings of Geoelectric values.

I took a few samples of melt rock -very heavy really.

I am posting a few photos of the crater.

I have another stone found at 2500 m on the bed
of a melt glacier, same story, that's not a stone
of the area, it is like a fuse, heavy and black
inside with a very aerodynamic shape, I will mail
you a photo ( after reading once more your
recommendations) if interested . for sure not a
human artifact or an original stone of the area.

Sorry to disturb,
...
=========================
I put the photos here:

http://meteorites.wustl.edu/meteorwrongs/libyan_crater.htm

The round thing in the desert looks something
like a crater. Maybe it's a bomb crater. Maybe
it's a meteorite impact crater. The rock doesn't
look like samples of Libyan desert glass that
I've seen. I don't know the LDG story well. Has
there ever been a crater associated with the glass?


Randy Korotev
Saint Louis, MO
korotev at wustl.edu


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Received on Wed 09 Dec 2009 03:47:49 PM PST