On Thu, 11 Sep 2003 20:01:18 -0500 In the thread "Cold hunting?" Sterling K. Webb, stated:
>Part of his figure of a fall rate only >2-1/2 times the MORP rate in his study >is the assumption that the Sahara has >always been as dry as it is now. The >wetter the Sahara actually was, the >greater the fall rate would have to be >to produce the existing survivor stones. > >I scrounged around and found a great >deal of substantial geological research >done in the Sahara before World War II, >when there was much freer access to the >area. Actually, there has been a significant amount of recent research. This and earlier research is summarized on a few web pages and available on-line. The best of them are: 1. AFRICA DURING THE LAST 150,000 YEARS by Jonathan Adams at; http://members.cox.net/quaternary/nercAFRICA.html http://www.esd.ornl.gov/projects/qen/nercAFRICA.html In that web page, Dr. Adams stated: "SAHARA (dates in Guo et al are given in 14C years ago on the left, approximate calibrated of 'real' dates are given on the right) Moist 9,500-8,200 14C ya (10,400-9,100 ya) Slight drying 8,200-8,000 14C ya (9,100-8,900 ya) Moist 8,000-7,000 14C ya (8,900-7,900 ya) Moderately dry 7,000-5,700 14C ya (7,900-6,500 ya) Moist 5,700-4,000 14C ya (6,500-4,500 ya) Very dry - as dry as at present - 4,000-3,800 14C ya (4,500-4,100 ya) Slightly moister than present 3,800-3,500 14C ya (4,100-3,700 ya) After 3,500 14C ya (3,700 ya). Remaining about as dry as at present" Guo Z., Petit-Maire N. & Kroepelin S. (2000). Holocene non-orbital climatic events in present-day arid areas of northern Africa and China. Global and Planetary Change. vol.26 pp.97-103. Also, there is: Claussen, M., Brovkin, V., Ganopolski, A., 2002, Africa: Greening of the Sahara. In: Steffen, W., Jager, J., Carson, D.J., Bradshaw, C., eds., pp. 125-128,Challenges of a Changing Earth. P roceedings of the Global Change Open Science Conference, Amsterdam, the Netherlands, 10-13 July 2001, SpringerVerlag, Berlin, New York. http://www.pik-potsdam.de/~claussen/papers/claussen+al_africa-hotspot_igbp_02.pdf "Sahara's Abrupt Desertification Started By Changes In Earth's Orbit, Accelerated By Atmospheric And Vegetation Feedbacks" at: http://www.sciencedaily.com/releases/1999/07/990712080500.htm Yours, Paul Baton Rouge, LA __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com ______________________________________________ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
