Meteorite Impact Fallback Breccia Ordovician Stromatolites

Name: Meteorite Strike Fallback breccia Stromatolites

Geological Time: Ordovician

Size: 4.5 by 3.9 inches

Fossil Site: Oneota Formation, Glover's Bluff, Wisconsin

This is unique stromatolite called impact fallback breccia. Coming from the Lower Ordovician, it is also very young, from a time when stromatolitic reefs no longer dominated the planet's marginal marine environments. Note the heterogeneous patterning with sharp and angular fragments of various size embedded in the reddish matrix. This beautiful pattern was formed during the so-called Glover's Bluff meteorite strike during the Ordovician; a fragment from the same meteor also struck in near Elm Rock Illinois, forming a mile-wide crater. The meteor that struck what is now the Oneota formation plowed through the stromatolite reef deep into the earth, spewing molten rock upward, with everything eventually falling back to earth, with one result being the "fallback impact breccia" seen here. It seems certain that the living stromatolite would have been decimated.

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