A site named fossilmall.com has pictures of the gunflint chert...and specimens for sale.
Dave F. eBay user ID mjwy and seller of stromatolites and classic meteorwrongs
Paul H wrote:
Discovery of distal ejecta from the 1850 Ma Sudbury impact event from "March Geology and GSA TODAY" media highlights at:
http://www.eurekalert.org/pub_releases/2005-02/gsoa-mga022805.php http://www.gsajournals.org/gsaonline/?request=get-current-toc&issn=0091-7613
Addison, W. D., and others, 2005, Discovery of distal ejecta from the 1850 Ma Sudbury impact event. Geology: Vol. 33, No. 3, pp. 193-196.
Addison et al. announce the discovery of impact ejecta from the Sudbury, Ontario, Canada, structure, the second largest and third or fourth oldest extraterrestrial Earth impact site. At 1.85 billion years old, these Paleoproterozoic ejecta are three times older than the previous oldest dated ejecta linked to a specific impact (Acraman, Australia, 0.59 billion years old). It is also larger than the well-known Chicxulub, Mexico (0.065 billion years old) impact linked to the extinction of the dinosaurs and many other species. The young Chicxulub impact, particularly its well-
preserved worldwide ejecta debris layers, have produced criteria to judge other large ejecta deposits. Foremost is the occurrence of sets of microscopic parallel lamellae in quartz and feldspar grains produced by the intense shock generated at the point of impact. Secondarily, the impact generated a megaplume of vaporized, melted, and crushed crustal rocks, creating molten droplets containing bubbles of gas, and larger accreted balls of dust and rock shards called impact accretionary lapilli. These features, and more, are seen in the Sudbury debris. The debris (ejecta) studied here, landed 650 km west northwest of Sudbury near Thunder Bay, Ontario, Canada, and 875 km west of Sudbury near Hibbing, Minnesota, United States. This huge impact likely deposited debris all around Earth, but it is very difficult to find because so much of the evidence has been destroyed in the recycling of Earth's crust by plate tectonics. Life at the time of the Sudbury impact was confined to the oceans and consisted of unicellular and colonial unicellular organisms. So far, Addison et al. have found no evidence of extinction of this life. However, future studies may link this impact and its ejecta with changes in the c
lassic Gunflint Iron Formation unicellular organisms and their photosynthetic microbial mats, which helped produce Earth's atmospheric oxygen.
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