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| | THE EARLY ARCHEAN RECORD OF LARGE ASTEROIDAL IMPACTS ON EARTH (Site not responding. Last check: 2007-10-10) |
 | | Initial evidence for very large impacts on the early Earth (Lowe and Byerly, Geology, 1986) was field and petrographic data from several unusual sedimentary layers in South Africa and Australia. |
 | | Recently, chromium isotopic anomalies were used to confirm an extraterrestrial component in these layers, to confirm the bolides were indeed of 20-50 km sizes, and to type one as a CV and another as untyped member of the carbonaceous chondrites (Shukolyukov et al., Impacts and the Early Earth, 2000; and Kyte et al., Geology, 2003). |
 | | All these impacts were large, comparable to those of Moon’s Late Impact Cataclysm (Tera et al., EPSL, 1974; and Ryder, Eos, 1990) at circa 3850 Ma, and likely had a profound influence on the course of physical and biological evolution on early Earth. |
| gsa.confex.com /gsa/2003SC/finalprogram/abstract_49146.htm (484 words) |
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