[meteorite-list] Re: hunting

From: Kelly Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:40 2004
Message-ID: <3AB6E93B.E96D9A1C_at_bhil.com>

Hi, Colin,
    When I wrote, I hadn't had the chance to check up on Qatar and the Gulf's
past, but you're right: it's the Arabian Plate's shallow interior basin, flooded
cyclically. That's where all the clay comes from, depositation in shallow seas
(also the limestone, shale and sandstone, if you got'em, and that stinky black
goo too, which we know you got).
    I could find references to the eastern Arabian peninsula margin being
flooded from 5 to 2 million years ago, then the current ice ages drew down
sealevels about 100+ meters below today's levels, uncovering the present coast,
but with every big interglacial, the sea level comes back up and floods again,
then drops again.
    Also, the plate motion (north with a clockwise twist) tilts your edge of the
plate up. The plate boundary's over inland in Iran 100 miles or more, so the
Gulf's an interior basin, perfect for clay deposits. A lot of the midwest of the
US is the same -- formerly flooded interior basin. You can drill through 700
meters of clay in some places around here (and sometimes find that stinky stuff,
but rarely enough of it). Lovely moasaur and whale fossils in Kansas. We got no
camels, though...
    To be on the safe side, I'd guess that during a glaciation Qatar would have
been a lot cooler and wetter than today, so perhaps you could only count on the
last 8000 years for really good preservation, which time period would have
accumulated about 1 stone per square kilometer. Of course, at this point, I'm
down to eyeballing estimates based on estimates based on... etc. Part of the
problem is that conditions would have cycled with the ice ages, see-sawing back
and forth.
    As for desert damage to meteorites, I have this little 30 gram Dhofar 020
from Oman that's a flattened shape. One face is eroded, chewed, crusted with
caliche and god knows what else, but flip it over and the rest of the stone is
perfect, good as new crust. Partial burial evidently protected it, at least
that's how I read it.
    McSween's book (Meteorites and their Parent Planets) has a photo of a 1993
find in the Jiddat al Harasis plain in Oman which is a limestone white pebble
desert. The chondrite is this big black pyramidal stone which sticks out like a
sore thumb. I mean, it does everything except get up and wave to be noticed.
Yet, within 20 meters, were the recent tracks of nine different motor vehicles,
none of whom had noticed the oddity of a big black stone alone in a snow white
desert. McSween says "it testifies to the low probability of meteorite discovery
by individuals not specifically looking for them."
    Yup, "In Search of Dilmun" is the book I meant, a fascinating story, even
though it was written about 50 years ago. A good mystery stays a good mystery
until it's solved, and I am a sucker for anything lost, lost cities, lost
empires, lost meteorites, you name it.
    Good hunting!

Kelly

colin wade wrote:

> HI Kelly
> I knew I could rely on you to crunch the numbers for me
> & thanks for raising some interesting points
>
> The predictions encourage further searching ,,, the dog runs for cover now
> if I reach for the metal detector & GPS !
>
> >From what Ive seen , the whole country was sea bed , the hills we have
> resulting from folds in the sandstone & chalk deposits .
> There are reported finds of shark teeth & flint arrowheads in the area (
> others have shown how easy it is to make a fresh arrow head & scatter them
> about ) But if people hunted here , presumably the wildlife would have had
> to survive without water tankers , & would require a food chain fron
> vegeterian to carnivore .
> The ground is remarkably fertile given a sprinkling of water ,& when wet the
> clay content swells & holds the moisture for ages , is the clay a sign of
> previous vegetation ?
> We had one year when the rain persisted so much , the local children were
> using inflatable dingies in the middle of the country , at the Shahania
> camel metropolis .The wild barley fruited twice that year .
> Since the loss of the vegetation the wind & sandstorms seem to be the force
> for geographic change , Ive even found a Rolls Royce with the paint
> sandblasted off one side ... so the chance of finding a good fusion crust is
> probably lottery numbers .
>
> The mention of Dilmun brings to mind our only visit to continental europe ,
> whilst in spain we met a lovely old lady & forgive me but the name has gone
> .... her brother did the illustrations for " in search of dilmun " , which i
> think was Bibby's work .She was quite thrilled that someone had heard of
> Dilmun , we had stayed at the hotel of the same name whilst in Baharain &
> they are keen on unearthing the ancient history .
>
> Thanks again for the info
> I'm off to bed to nurse my second cold of 2001 .( puttin a lump o'meteorit
> under the pillow to see if it cures it )
> all the best
> col
Received on Tue 20 Mar 2001 12:23:08 AM PST