[meteorite-list] The Pairing Problem

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:37:33 2004
Message-ID: <3A316C59.A5798422_at_lehrer1.rz.uni-karlsruhe.de>

MARVIN U.B. (1989) Meteorite distributions at the Allan Hills main
icefield and the pairing problem (In Field and Laboratory Investigations
of Meteorites from Victoria Land and the Thiel Mountains region,
Antarctica, 1982-1983 and 1983-1984, eds. U.B. Marvin and G.J.
MacPherson, Smiths. Contrib. Earth Sci. 28, 113-119):

Conclusions

This study shows that distribution patterns of specimens on the
Antarctic ice sheet can be a helpful guide to meteorite pairings, but
one that always must be used in conjunction with other types of
evidence. Laboratory examinations confirmed the main outlines of field
pairings for some of the seven meteorite classes discussed herein, but
produced numerous surprises when adjacent specimens proved not to belong
to the same fall and widely separated ones showed strong evidence that
they did belong together. Meteorites that fall close together are, in
general, expected to remain close together while being transported
within a large ice sheet. Confusion begins when they emerge from the ice
and are mixed with other meteorites on stranding surfaces that are
compressed against mountain barriers by the persistent push of the
oncoming sheet. Furthermore, the powerful storm winds of Antarctica can
send specimens up to cobble size - and probably boulder size -
skittering across the ice to new locations, and drifts of snow cover and
uncover different groups of specimens from season to season. Despite all
the factors that disturb the orderly patterns of strewnfields, specimen
distributions are of sufficient aid in pairing to make mapping worth the
effort.
Since the 1982-1983 season, mapping techniques have been speeded up and
made more accurate by use of an infrared distance measuring device to
determine geodetic positions of meteorite specimens relative to known
points. There will be no further need for painstaking attempts like this
one to superimpose maps in order to locate find sites. However, the
first six seasons at the Allan Hills Main lcefield yielded a unique body
of data that demanded analysis.


Best wishes,

Bernd
Received on Fri 08 Dec 2000 06:18:49 PM PST