[meteorite-list] New Iron (Ataxite) SHRAPNEL

From: info at niger-meteorite-recon.de <info_at_meteoritecentral.com>
Date: Tue, 22 Jun 2010 09:26:51 +0200 (CEST)
Message-ID: <71736143.94882.1277191611737.JavaMail.open-xchange_at_oxltgw02.schlund.de>

Dear Richard, Doug, others,
?
while the crater floor indeed seems to be covered by wind borne sand deposits we
should take note that the surrounding surfaces are composed of coarser material,
most probably some sort of desert pavement, which in turn covers a coarser
weathering layer of the underlying bedrock (my guess is Eocene limestone). Wind
borne sand is present leeward of outcrops and in the gullies, but on the
deflation plains its presence is limited to the interspaces of the small pebbles
forming the top surface.
?
Although to a lesser extent than the sandstone bedrock of the Uwaynat or the
Gilf Kebir, the exposed Eocene limestone rock of the nearby outcrops has
developed darkening due to the forming of desert varnish. This is a practicable
indicator for relative surface ages on sat images for the general area. The
gullies of the drainage system show brighter colors, due to their relatively
young Holocene formation. The deflation areas with undisturbed desert pavements
show an intermediate darkening. The dark grey hue of the coating on the desert
pavement can be seen best east of the gully running north to south approx. 120
meters east of the crater.
?
The ejecta rays, and I am convinced this is what we are looking at here, are of
a brighter color, indicating less darkening of the material by desert varnish
and a more recent formation compared to the deflation plain on top of which it
came to rest. The borders of the ejecta blanket are actually quite crisp,
particularly east of the crater where one can see the eastern ejecta ray cutting
across the gullie and into the undisturbed desert pavement.
?
When zooming into the image, it also becomes obvious that the ejecta material,
at least in the ray pointing to the southeast, includes coarser bedrock
material, very much like the material which can be seen in the crater rim. The
bright patches of ejecta material in the north and northeast of the crater are
most probably composed of larger fragments too. No silt or sand deposit would
last very long on top of these plains since the intense winds in the area blow
almost 300 days a year (and from the same direction).
?
To get a picture of the intense forces shaping this incredible landscape one may
inspect the sharp-crested Seif-dunes (after the Arabic word for ?sword?) which
formed parallel to the prevailing wind direction in the lee of an outcrop ~ 3 km
to the northwest of the crater).
?
Zooming out the sat-image, one notes that the general wind direction in the area
is north by northeast to south to southwest. Thus, any Aeolian deflation or wind
shaped sedimentation pattern around the crater would have to be oriented along
this axis. This appears not to be case. Instead we see a radial pattern with the
crater as its center.
?
Once again the link to the crater site to compare:
?
http://maps.google.de/maps?f=q&source=s_q&hl=de&geocode=&q=26%C2%B0+05%27+16%22+E,+22%C2%B0+01%27+6%22+N&sll=50.234524,12.885482&sspn=0.007974,0.01929&ie=UTF8&ll=22.018379,26.087661&spn=0.001445,0.002411&t=h&z=19
?
?
Cheers,
Svend

Richard Kowalski <damoclid at yahoo.com> hat am 21. Juni 2010 um 22:37 geschrieben:

> Mike and Doug. Cool beans!
>
> Doug, I'd be hesitant to call those rays, especially considering how full of
> sand the crater is, any rays would probably have been covered or destroyed
> long ago. (Rays are somewhat fragile)
>
> I zoomed into the crater in Google Earth with a horizontal view, exaggerating
> the relief to the maximum setting and it appears the crater is on a gentle
> slope, higher to the north east and lower to the south and west. The rim is
> very low, at least as displayed in GE.
>
> I'd guess the apparent rays are just due to windblown sand and dust shaped by
> the profile of the rim itself.
>
> Are there any photos from ground at the site available?
> Since it is a disputed zone, I doubt any higher resolution aerial images will
> become available any time soon, but someone may want to custom order a
> satellite image of the area.
>
> --
> Richard Kowalski
> Full Moon Photography
> IMCA #1081
>
>
> --- On Sun, 6/20/10, Mexicodoug <mexicodoug at aim.com> wrote:
>
> > The crater itself is relatively small and a
> > 10 minute walk from the Sudan and not too far from Libya,
> > for those who would enjoy a safer GooglEarth trek for the
> > the impact crater can look here in the Gilf Kebir zone
> > (22?01'6"N, 26?05'16"E). This is a real crater with real
> > meteoritic shrapnel, not borderline, even look at the rays
> > which are still there from the impact !
>
>
>
>? ? ? ?
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Received on Tue 22 Jun 2010 03:26:51 AM PDT