HR: 08:25h
AN: PP41A-02    [Abstracts]
TI: Extraterrestrial Markers Found at Clovis Sites Across North America
AU: * West, A
EM: allen7633@aol.com
AF: GeoScience Consulting, P.O.Box 1636, Dewey, AZ 86327, United States
AU: Firestone, R B
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94710, United States
AU: Kennett, J P
AF: Univ. of California, Santa Barbara, Dept. of Earth Sciences, Santa Barbara, CA 93106, United States
AU: Becker, L
AF: Univ. of California, Santa Barbara, Institute of Crustal Studies, Santa Barbara, CA 93106, United States
AB: We present evidence for an extraterrestrial (ET) impact event with Earth at about 12.9 ka, which, we hypothesize, caused abrupt environmental changes that contributed to Younger Dryas (YD) cooling, major ecological reorganization, broad-scale extinctions, and the rapid human behavioral shifts evident at the end of the Clovis Period. Terminal Clovis-age sites in North American are marked by a thin, discrete layer, the YD boundary layer (YDB) with varying peak abundances of an array or ET markers, including magnetic grains, microspherules, carbon spherules, soot, fullerenes with ET helium, and iridium. We will present data from a number of well- known Clovis sites and other locations in support of the YD impact event. Gainey, north of Detroit, Michigan, is a PaleoAmerican campsite that was located a few tens of kilometers from the southern margin of the Laurentide Ice Sheet at 12.9 ka. Gainey gave its name to the distinctive fluted point style found there, and Gainey sediments contained some of the highest abundances of YDB markers found, suggesting that the YD impact was centered nearby. Murray Springs, near Sierra Vista, Arizona is one of the best known Clovis mammoth kill-sites. A distinctive carbonaceous layer, called a "black mat" and thought to be of algal origin, drapes conformably over the mammoth bones (Haynes and Huckell, 2007). A thin layer (about 2 mm), the YDB, containing Younger Dryas impact event markers, lies at the base of the black mat and immediately overlies the mammoth bones and Clovis artifacts. Blackwater Draw, New Mexico is southwest of the town of Clovis, which gave its name to the type of projectile points first found there. It was a PaleoAmerican hunting site on the bank of a spring-fed waterhole, and the black mat drapes over bones of butchered mammoths and Clovis artifacts. Topper, located on a high bank of the Savannah River near Allendale, South Carolina, was a Clovis-age flint quarry containing thousands of artifacts. YDB markers occur within an approximate 5-cm interval immediately above the distinct layer of Clovis artifacts. Wally`s Beach at St. Mary Reservoir, southwestern Alberta, Canada, at 12.9 ka, supported many species of now-extinct megafauna, including mammoths, camels, and horses (Kooyman, et al., 2001). YDB markers, including iridium at 51 ppb, occur inside an extinct horse skull at the Wally's Beach Clovis kill-site, suggesting rapid burial following the YD event. One other Clovis site examined was the Chobot site near Edmonton, AB, Canada. We also examined other sites that date to 12.9 ka: glacial Lake Hind in MB, Canada; an ice-aged drumlin at Morley, AB, Canada; Daisy Cave on the Channel Islands of California; and Lommel in Belgium. At all sites, the YDB layer was evident, dated to around 12.9 ka, and contained abundant ET markers.
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 6022 Impact phenomena (5420, 8136)
DE: 6240 Meteorites and tektites (1028, 3662)
DE: 6250 Moon (1221)
DE: 9350 North America
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly