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The Allan Hills Meteorite Icefield-An alternative view

Annexstad, J. O. and Schultz, L. and Epstein, S. (1983) The Allan Hills Meteorite Icefield-An alternative view. Meteoritics, 18 (4). p. 260. ISSN 0026-1114. https://resolver.caltech.edu/CaltechAUTHORS:20140909-095309928

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Abstract

More than 1300 meteorites have been found on the surface of blue icefields in North Victorialand, Antarctica. The Allan Hills Icefield (about 100 km^2) has exceptionally high meteorite concentrations while other icefields to the West have much smaller concentrations. Measurements of the rates of ablation and of horizontal displacement of the ice surface near the Allan Hills have been conducted since 1978 at a 20 station triangulation network. These data show that the horizontal ice velocity at the most active stations is about one m/yr and less at the high meteorite concentration site. Ablation of the ice surface averages about 4.2 em/yr. Measurements of the oxygen isotopic composition of surface ice along the triangulation network show a rather large scatter of about 8δ^(18)O‰. This indicates that the ice comes from different areas or possibly is different in age. The terrestrial ages of Allan Hills meteorites are between 0 and 700,000 years, with only a few older than 400,000 years. A model for the appearance of meteorites on blue ice surfaces in Antarctica is that specimens are carried within the moving ice sheet to stagnant areas where they are uncovered by the ablation process (see e.g. Bull and Lipschutz, 1982). These areas ("emergent zones") are fed by ice that originally accumulated as snow at the source regions of the ice. This model accounts for the general occurrence of meteorites on blue ice fields but an additional mechanism is needed to explain the high concentrations found at the Allan Hills. It is suggested that this icefield has concentrated meteorites primarily by horizontal movement of the ice from the emergent zones located to the west of the concentration zone. These meteorites are transported by surface compressive flow of the ice into the Allan Hills Meteorite Icefield and left stranded in an area where ice is only lost by the ablation process. This model seems to be in agreement with all field and laboratory observations.


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http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.1983.tb00194.x/abstractPublisherArticle
http://dx.doi.org/10.1111/j.1945-5100.1983.tb00194.xDOIArticle
Additional Information:© 1983 Meteoritical Society. Provided by the NASA Astrophysics Data System.
Issue or Number:4
Record Number:CaltechAUTHORS:20140909-095309928
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140909-095309928
Official Citation:(1983), ABSTRACTS OF PAPERS PRESENTED AT THE 46th ANNUAL MEETING THE METEORITICAL SOCIETY SEPTEMBER 5–9, 1983 MAINZ, FRG. Meteoritics, 18: 259–433. doi: 10.1111/j.1945-5100.1983.tb00194.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49489
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 Sep 2014 18:35
Last Modified:03 Oct 2019 07:14

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