[meteorite-list] Finding fossil Meteorites

From: MEM <mstreman53_at_meteoritecentral.com>
Date: Mon, 25 Oct 2010 16:17:33 -0700 (PDT)
Message-ID: <797025.91491.qm_at_web55205.mail.re4.yahoo.com>

Hello Bernd,
I believe those numbers are from a specific incident and may have been those
found in the tiles on the floor where they were first identified by an astute
geologist attending a function there. They were subsequently traced back to one
quarry ( Brunflo?) Subsequently many more were found at several quarries in
Sweden.

I agree regarding the mineralogy of fossil meteorites and probably depletion of
expected elements. Knowing what I think I know about typical meteorite fabric,
deep weathering, taphonomy , and secondary mineral formation(wink wink) any
fossil meteorite will likely be depleted of the normal, hallmark,
minerals/elements via normal leaching. For example, I think nickel is more
mobile than we ordinarily believe and it will probably be carried away to form
the microscopic hair-like crystals ( aka accular) of the mineral "millerite" or
even a nickel carbonate gaspetite(?) which might be missed on casual
observation. Another example might be the pyroxines. They weather into a very
"non-mineral looking" flexible sheet of the mineral palygorskite also know as
mountain cork/leather, and so on. Fossil meteorites may retain meteorite
character in composition or in form with no original mineralization or easily
recognizable meteoric shale ( e.g. Sardis Iron, Georgia, USA). I'd be curious
as to the nickle content of that shale, or Lake Murry shale compared to Lake
Murry iron proper. That should give a glimpse into migration tendencies of
siderophile elements out of the matrix over a span of 115 million years anyway.

I have not attempted to compile a list of secondary mineralization for the
minerals found in meteorites but, thinking into what the associated minerals
might be and, how they form is intriguing, as another diagnostic clue into
bombardment rates in the past.


 I recall a study into past bombardment rates, and the Ordovician was one marked
by high impact rates. In fact just this week was a report that a 120km
crater/(cluster of craters) of Ordovician age was found in Australia. I know
there were several major impacts in the Cretaceous well before Chuxilub and I
seem to recall a higher rate of bombardment in the Carboniferous as well.

I believe that there are relatively lots of fossil meteorites in situ only the
people most closely connected with exposing them aren't looking for meteorites.
They just hit "bad rock" and send it to the dregs/crushing pile and move on.
The candidate specimens I've collected, were found because I spent a lot of time
in the field and in the books and kept a look out for rocks that somehow didn't
fit the normal for where they were found. Pretty much how we hunt surface
meteorites.

Back to the limestone quarry(s) where the Ordovician specimens were found in
Sweden. There have been many found at different quarries in there and probably
reflect sustained worldwide bombardment in my opinion owing to the successive
depths they were found at.
<http://epsc.wustl.edu/~visscher/research/fossil_files/frame.htm>

 I believe many were discarded prior to the recognition that they were
meteorites. The layer they were concentrated in made for poor polishing and
hauled off to a remote section of the quarry for crushing. I believe the report
of 3-5-8 or whatever the number, was the number originally found in the
marble/limestone tiles on the floor of a building where an astute visitor
recognized them as such. They were then tracked back to the quarry. I thought
about 60 or more were recovered , the article says 25 from a particular quarry.

 Here is a blurb from a web page.
<http://www.science-frontiers.com/sf125/sf125p07.htm>

Fossil Meteorites
Over a century ago, astronomer H.W.M. Olbers (of Olbers Paradox fame) remarked
that meteorites are extremely rare in the fossil record. While meteorites are
found in profusion in some specially favored surface deposits (Antarctica and
Australia's Nullarbor Plain), there are very few records of any being found in
the immense volumes of coal, gold ores, and other geological materials that
have been mined down the centuries. Of course, many meteorites escaped the
notice of miners who were looking for something else. Nevertheless, few have
been reported from strata more than a few thousand years old. (See ESI8 in
Neglected Geo logical Anomalies.) It is therefore surprising that a veritable
lode of fossil meteorites has been found in a limestone quarry at Kinnekulle,
in southern Sweden.

"During the sawing of a few thousand cubic meters of Ordovician limestone into
2-3 cm thick slices, 25 fossil meteorites have been found. All meteorites,
except, four, have been found in a 60 cm thick bed called the Archaeologist.
This bed represents a few hundred thousand years and contains several hard
ground surfaces...Many of the Archaeologist meteorites are prominently angular
in shape whereas others are round. This seems difficult to reconcile with an
atmospheric breakup of a single large meteorite."

B. Schmitz and M. Tassinari, the authors of this paper, suggest that this rare
concentration of fossil meteorites represents an unusual event in the solar
system history, possibly a major collision in the asteroid belt.

(Schmitz, Birger, and Tassinari, Mario; "Early Ordovician Meteorites: How Many
Falls?" Eos, 79:F50, 1998.)

Comment. It should be added that tektites and microtektites (impact debris) are
likewise found mainly in recent, superficial deposits, even though many ancient
impact craters are now recognized on earth.


Finally, I note a site for catalogs of scientific anomalies which includes the
Ordovician Meteorite Occurrences in Sweden.
<http://www.science-frontiers.com/sourcebk.htm>

Regards
Elton

----- Original Message ----
> From: "bernd.pauli at paulinet.de" <bernd.pauli at paulinet.de>

> Considering the high degree of terrestrialization of Ordovician/fossil
>meteorites
> (usually the chromite content is the only hint it once was meteoritic) and
>also
> considering the extremely low number (5 or 6?) of fossil meteorites found so
>far,
> it is highly unlikely a meteorite collector will ever find a fossil meteorite
>in situ.
>
> Regards,
>
> Bernd
>
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Received on Mon 25 Oct 2010 07:17:33 PM PDT