[meteorite-list] Question About Potassium-Argon (K/Ar) dates forNorth American and Australasian Tektites

From: Paul <bristolia_at_meteoritecentral.com>
Date: Thu, 16 Oct 2008 12:20:15 -0700 (PDT)
Message-ID: <156634.65823.qm_at_web36208.mail.mud.yahoo.com>

Sterling K. Webb wrote:

>Are these "alleged tektites" that you refer to the
>ones found in Glenmora, Rapides Parish, that were
>reported on by King in 1970?
>http://adsabs.harvard.edu/abs/1970Metic...5Q.205K
>No abstract or paper available. I guess these
>tektites are not popular.

Yes, they are the ones that I referred to.

>Former (?) List member Ed Albin:
>http://www.lpi.usra.edu/meetings/LPSC99/pdf/1357.pdf
>"King [1968] described a bediasite find within the
>upper Eocene Wellborn Formation in Grimes County,
>Texas. This deposit has been traced eastward and
>correlates with the Yazoo Clay Formation in Louisiana,
>Mississippi, Alabama, and the Dry Branch Formation
>in Georgia. It is entirely possible that North American
>tektites may eventually be recovered from upper
>Eocene deposits between Georgia and Texas."
>
>But were King's tektites North American tektites in
>composition? Wetback Bediasites, as it were?

According to King (1970), their composition was
identical to certain Australites. They also were
dated by K/Ar dating to about the same age as
Australites. Therefore, they clearly are not North
American strewn field tektites. I expect that when
someone looks at the right outcrop, that tektites
of the North American strewn field will be found
in either Eocene strata of the right age or
redeposited in younger Pliocene or Pleistocene
gravels within Louisiana.

>In 1986, leading geochemist Cristian Koeberl
>said the King tektites from Louisiana were Australites:
>http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.ea.14.050186.001543?journalCode=earth
>I can't get to that paper, naturally.

Again, that is what King (1970) concluded from
composition and K/Ar dating. The tektite examined
by King (1970) was one of two specimens sent him
by an unnamed "Louisiana rancher" as possible
meteorites. The rancher said that he had found
it and two other similar specimens at a "local"
gravel pit in 1965.

>I can get to this paper by Koeberl (and so can
>everybody else on the List). It's his analysis
>of the Cuban "tektite" which proved to be a
>member of the North American strewnfield:
>http://adsabs.harvard.edu/full/1988Metic..23..161K
>but I can't pull a quote out as the paper's a page
>image, not text. The gist of Koeberl's remark is
>that the "Cuban" tektite is genuine, in distinction
>to King's tektites which were "allergedly" found in
>Louisiana, were then discovered to be Australites,
>and therefore could not have come from Louisiana.
>He said that they were a fraud, in other words.
>The tektites are tektites, but is the find a find
>in Louisiana?

The problem, as I have discovered doing archaeology,
is that people can be vary careless in keeping track,
what specimen was found and where it was and what
specimens were bought and where they were bought.
Unfortunately, some collectors of artifacts, fossils,
rocks, and tektite get their specimens mixed up and
lose track of what was found where. It was 5 years
between when the specimens were reported to have
been found and King's paper. One possibility is that
the collector lost track of where and how he
originally obtained the specimens. The question is
one of human carelessness that abounds among some
collectors.

There is the archaeological site in Hawaii where
hundreds of European Paleolithic artifacts were found
that shows how prehistoric materials have been
unintentionally moved about by humans in historic
times. How that happened is another story that is
quite instructional about how stuff gets misplaced
around the world by accident.

>but is the find a find in Louisiana?

That is the key question as King (1970) pointed out.

>What Koeberl was not aware of is that some years
>later Alan Hildebrandt (another geochemical
>authority) found some Australities in and around
>Tikal, the ancient Mayan city in Guatemala adjacent
>to the Yucatan. On the global scale, Louisiana and
>the Yucatan a mere tektite's throw apart, and both
>roughly antipodal to the Australasian strewnfield.

The Tikal tektites are unexplained. They consist
of 11 "nodules" found among obsidian tools in
various parts of the Tikal site, Guatemala. Unlike the
"Louisiana tektites", they were found during
archaeological excavations. Thus, it is known that
they are "in situ" at least within the region within
prehistoric times. It has been suggested that they
are tektites of the Muong Nong type. Also, they have
been Ar/Ar dated at 800,000+/-100,000 BP. Nothing
like them has been found at any other site or parts
of Central America. The Tikal tektites, like any
other tektite, continue to defy any attempt to
explain them.

A Couple Tikal tektite references:

Nagy, H. M.,2002, Tikal Report 27B: The Artifacts
of Tikal : Utilitarian Artifacts and Unworked
Material, University of Pennsylvania Museum
Publication, Philadelphia, Pennsylvania

Hildebrand, A. R., Moholy-Nagy, H., Koeberl, C.,
May, L., and others, 1994, Tektites found in the
ruins of the Maya city of Tikal, Guatemala. Lunar
and Planetary Science, vol. 77, pp. 213-219.

>If this is the case, then no amount of analysis of
>the "alleged" tektites is meaningful -- they are
>tektites!

I agree with King, Koeberl, and you that they are
tektites. The problem, which King (1970) also discusses,
is that it is uncertain whether these tektites came from
Louisiana or not.

>You would need instead need to investigate the
>circumstances of the find, the character and motives
>of the finder. This would seem to be a difficult goal
>to pursue definitively after a 38 year lapse.

That is what I have been doing off and on for a couple
of years. Having checked NASA, University of Houston,
king's daughter, and many other places, I found that
all of the field notes, laboratory notes, pictures,
maps, and specimen(s) related to King (1970) have
apparently been lost. Nobody, whom I have contacted,
know where these materials are. If anyone has any ideas
where these materials might be / can be found, please
drop me a note off-list with your ideas and suggestions.

>But if they are (both) Australites and were discovered
>in situ, that in itself is major news (or an inconvenience
>to be ignored, of course), like the Ivory Coast tektite
>(identified by analysis in 1982 by Shaw and Wasserberg)
>found off the coast of Australia in the sea bed. (Currents?
>Yeah, sure...)
>
>If Koerberl said the Louisiana tektites were real
>(and Australites), then they were tektites. No question.
>Better go find some more! Did anybody record the exact
>location of the find?

Apparently Dr. King did know as he and "three field
assistants" spent three days at the gravel pit looking
for more tektites and found none. While, talking with
people, I found that his daughter also accompanied
them to look for tektites. However, she did not
remember anything about the pit's location. Unfortunately,
any field or personal notes and maps about the exact
location of the gravel pits have apparently all been
either misplaced or discarded and utterly lost for any
practical purposes. Without this information, it is
impossible to find out who the "Louisiana rancher" was
and check to see if he might have either any more
specimens or information.

Another problem is that the gravel pits around Glenmora,
Louisiana have been largely reclaimed. Thus, even if we
knew exactly where the gravel pit was located, very
likely there would be nothing except grass and ponds to
look at.

If a person applies what is known about the local
geomorphology and Pleistocene sediments, there is a
specific ?stratigraphic? horizon where a person can
expect to find them, if they exist. That is where I am
looking for them. Also, I have contacted knowledgeable
people have, after a fashion, have been looking over
the locations where any tektites might be found
around Glenmora on a regular basis for decades. What
they have and have not found does say something
about whether Louisiana tektites might exist. The
specific details of the above part of the story are
best told at another time and in another venue.

Yours,

Paul H.


      
Received on Thu 16 Oct 2008 03:20:15 PM PDT