[meteorite-list] Discovery of distal ejecta from Sudbury impact event

[David Freeman]

"...unicellular organisms" "...photosynthetic microbial mats" AKA 
"stromatolites".
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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