Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Apr 26, 2012 17:11:25 GMT -5
Morsefire, I know they now suspect that the astroid that crashed into Sudbury threw off ejecta that landed on top of the BIF formations in Minnesota, effectively stopping their formation. At least for a time. In a complicated way though, not just by capping them. I may also have simplified my explanation a bit too much. The banding occurs from changing levels of acidity of the water and oxygen levels in the atmosphere/water. These levels were not just effected by cyanobacter, but before and after that by volcanic activity, and also even by things like the extent of glaciation, purple bacteria and other possibilities.
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morsefire
noticing nice landscape pebbles
Member since November 2011
Posts: 83
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Post by morsefire on Apr 27, 2012 6:33:49 GMT -5
Dan, this is why I have fell in love with these rocks. Pretty amazing theories on their creation and they are beautiful. When I'm hunting in my favorite pits and dumps it's so hard to decide who to take home!
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