Rock Elm Disturbance

The Rock Elm Disturbance is an impact crater in Wisconsin, United States, roughly 40 kilometres southwest of Menomonie. The disturbance is named for Rock Elm, Wisconsin, a nearby community.

The meteorite is estimated to have been 170 m in diameter with a mass of 9×109 kg and impact velocity of 30 km/s . The crater is 6 km in diameter, and fossils found in the rock filling the crater suggest it dates to the Middle Ordovician Period, about 455 to 430 million years ago.
It may be one of several Middle Ordovician meteors that fell roughly simultaneously 469 million years ago, part of a proposed Ordovician meteor event that includes the Decorah crater in Iowa, the Slate Islands crater in Lake Superior, and the Ames crater in Oklahoma.

Wikipedia