[meteorite-list] Fw: Still un answered question
From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 10 Jan 2008 14:46:16 -0600 Message-ID: <009f01c853c9$d8956360$795fe146_at_ATARIENGINE> Hi, Jerry, List, The meteorites of Roosevelt Co. are found in wind-ablated pits, called "blow-outs," which fill with sand and preserve them. http://epswww.unm.edu/meteoritemuseum/nmmeteorites.htm The age of the surfaces that are being searched? 50,000 to 90,000 years old! http://adsabs.harvard.edu/abs/1992Metic..27..460Z The abstract: "We have obtained minimum age estimates for the sand units underlying the two largest meteorite deflation surfaces in Roosevelt County, New Mexico, USA, using thermoluminescence dating techniques. The dates obtained ranged from 53.5 (+/- 5.4) to 95.2 (+/- 9.5) ka, and must be considered lower limits for the terrestrial ages of the meteorites found within these specific deflation surfaces. These ages greatly exceed previous measurements from adjacent meteorite-producing deflation basins. We find that Roosevelt County meteorites are probably terrestrial contemporaries of the meteorites found at most accumulation zones in Antarctica. The apparent high meteorite accumulation rate reported for Roosevelt County by Zolensky et al. (1990) is incorrect, as it used an age of 16 ka for all Roosevelt County recovery surfaces. We conclude that the extreme variability of terrestrial ages of the Roosevelt County deflation surfaces effectively precludes their use for calculations of the meteorite accumulation rate at the Earth's surface." The full PDF: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1992Metic..27..460Z&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Another area similar to Roosevelt Co. is described and the mechanism of preservation is given in more detail: https://e-reports-ext.llnl.gov/pdf/237492.pdf "Most meteorites from this area have been found on the floors of active deflation basins (blowouts) that have been excavated from a mantle of sand dunes. This area has no apparent fluival or permafrost activity within the last 50,000 years [e.g., 4,5], suggesting that only prevailing winds and natural aridity aid in the concentration and preservation of meteorites." Has anyone searched this area (Lea Co., NM) further? (Did it "pan out"?) Sterling K. Webb --------------------------------------------------------------------- ----- Original Message ----- From: "Jerry" <grf2 at verizon.net> To: "meteoritelist meteoritelist" <meteorite-list at meteoritecentral.com> Sent: Thursday, January 10, 2008 2:10 PM Subject: [meteorite-list] Fw: Still un answered question Jerry Flaherty ----- Original Message ----- From: "Matson, Robert D." <ROBERT.D.MATSON at saic.com> To: "Jerry" <grf2 at verizon.net>; "Peter A Shugar" <pshugar at clearwire.net>; "LIST" <meteorite-list at meteoritecentral.com> Sent: Thursday, January 10, 2008 1:39 PM Subject: RE: [meteorite-list] Still un answered question Nope. Just *ONE* meteorite hunter -- Skip Wilson -- a very methodical and thorough one. "A meteorite every 22.5 square miles" doesn't really tell the story -- Skip searched (continues to search?) a much smaller area than this, but he is very selective about the surfaces searched. In ideal locations, the meteorite density is much, much higher than 1 per 22.5 square miles. If the average terrestrial lifetime of a meteorite is, say, 5000 years, the expected density is more like 3 meteorites per square mile. --Rob P.S. Feel free to forward this to the meteorite list. You'll see that I included it in the "To" list, but I guarantee it won't show up there. -----Original Message----- From: meteorite-list-bounces at meteoritecentral.com [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Jerry Sent: Thursday, January 10, 2008 9:25 AM To: Peter A Shugar; LIST Subject: Re: [meteorite-list] Still un answered question Sounds like ideal search conditions and a hulava lot of meteorite hunters. Jerry Flaherty ----- Original Message ----- From: "Peter A Shugar" <pshugar at clearwire.net> To: "LIST" <meteorite-list at meteoritecentral.com> Sent: Thursday, January 10, 2008 12:04 PM Subject: [meteorite-list] Still un answered question > Still unanswered is the other question: > And then there is little dinky Roosevelt Co, NM at just 2,455 sq miles and > it has a staggering 109 meteorites, which comes to one for every 22.5 sq > miles. What gives? > They are of a wide variety of classifications, so it can't be turning > every piece in > for classification. I can't speak for anyone else, but I find this very > puzzling. > Any thoughts, List? > Pete > ______________________________________________ > http://www.meteoritecentral.com > Meteorite-list mailing list > Meteorite-list at meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list at meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list at meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Thu 10 Jan 2008 03:46:16 PM PST |
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