Wednesday, December 23, 2009

Yet another interesting meteorite story

We already had a recent blog post on the possible "real" meteorite crater, which is thought to be responsible for the events marking the K/T Boundary. Now here is another interesting meteorite story: Geology recently published a paper on a hypothesis that the Sudbury Impact caused the end of banded iron deposition, at least in the Lake Superior region.

The authors note that in the Lake Superior region of North America, deposition of most banded iron formations (BIFs) ended abruptly 1.85 Ga ago, coincident with the oceanic impact of the giant Sudbury extraterrestrial bolide. In their paper Slack and Cannon propose a new model in which this impact produced global mixing of shallow oxic and deep anoxic waters of the Paleoproterozoic ocean, creating a suboxic redox state for deep seawater. This suboxic state, characterized by only small concentrations of dissolved O2 (~1 ยตM), prevented transport of hydrothermally derived Fe(II) from the deep ocean to continental-margin settings, ending an ~1.1 billion-year-long period of episodic BIF mineralization.

Slack, John F., und William F. Cannon (2009), Extraterrestrial demise of banded iron formations 1.85 billion years ago, Geology, 37(11), 1011-1014, doi:10.1130/G30259A.1.

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