[meteorite-list] Finding fossil Meteorites

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 25 Oct 2010 22:04:11 -0500
Message-ID: <A5F8ECA75DF342B8A8E2077A02D38127_at_ATARIENGINE2>

There are a number of impact and possibly impact related
events going on in the solar system in this time frame of
480 mya back to 570 mya. (Mya = million years ago.) Far
more events than in most time periods of that length.

1. The density of fossil meteorites in the Swedish quarries
indicate a fall rate approximately 120 (+/- 50) times that
of the present day over a period of at least 2 my.

2. The distribution of impact glass spherules in lunar soil
indicate that the inner solar system impact rate, having
declined asymptotically since 3800 mya, began to rise at
600 mya and peaked about 420 mya at a rate not seen for
3 billion years. It's still at this rate, with some evidence
(disputed) for another increase about 100 mya.

3. The largest asteroidal breakup of the past few billion
years occurred about 500 (+/- 100) mya, the Flora family,
believed to be the source of the Ordovician fossil meteorites.
As Chris pointed out, the age of L-chondrites corresponds
to this same time period with great exactitude (465 +/-
15 mya).
    8 Flora is a 130-km body, the innermost large asteroid.
No asteroid as close to the Sun as Flora has a diameter
above 25 kilometers. Flora's orbit is in the Ecliptic plane
(5.5 degrees inclination). Flora has a composite surface
(L-chondrite and nickel-iron). The size of the "original"
pre-breakup Flora is unknown. Essentially, Flora is/was
the closest major asteroid to the inner solar system, where
things are happening.

4. Between 480 mya and 620 mya, the Earth had three
large-scale glaciation episodes (the 2nd, 3rd, and 4th largest
of its history, one of which was the "Snowball Earth" glaciation
in which ice may have covered (or almost covered) the entire
planet, land and sea, to the equator. In addition, there was
an episode of rapid axial tilt re-orientation so fast and large
that it's hard to accept the claim, although the evidence for
it is remarkably good. It's just hard to wrap your head
around it.

5. The total re-surfacing of the planet Venus is dated by the
crater-count method to 480 (+/- 60) mya. Totally resurfacing
an entire terrestrial planet, over-turning the crust and melting
at least the upper portion of the mantle, requires the impact
of materials whose total mass is roughly equal to a 300+ mile
body at an absolute minimum. As there is no coherent
"geological" explanation for re-surfacing an entire planet,
impact would seem to be the default.

    All the evidence of these events are confined to the crowded
inner solar system. There is no indication (that we know of) of
large-scale impacts or planetarily significant events in this
period for Mars or any outer system objects.
    What we have is an assemblage of evidences of major events,
some fairly explainable and others much more obscure. The
close association of so many "catastrophic" events with this
fairly specific period of time is unlikely to be a coincidence.
Some connection between these events is more likely than
not.
    The most energetic of these possible events would have
to be the Venus re-surfacing and crust/mantle melting by
impact. This would leave the other events to be "blowby" of
that event, even the Flora breakup. Something happened.
Past that, it's speculation.


Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: "MEM" <mstreman53 at yahoo.com>
To: <bernd.pauli at paulinet.de>; <Meteorite-list at meteoritecentral.com>
Sent: Monday, October 25, 2010 6:17 PM
Subject: Re: [meteorite-list] Finding fossil Meteorites


> 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 11:04:11 PM PDT