The Alamo bolide impact occurred 377–378 million years ago, when one or more hypervelocity objects from space slammed into shallow marine waters at a site that is now the Devonian Guilmette Formation of the Worthington Mountains and Schell Creek Range of southeastern Nevada; the event is named for breccias of metamorphosed crushed rock deposits, found near the town of Alamo, Nevada (the "Alamo Breccia"). This catastrophic impact event resulted in what is one of the best-exposed and has become the most accurately dated impact events; it occurred within the Frasnian age of the Devonian at about 377-378 Ma, a moment in time that was about 5.9 Ma prior to the Frasnian/Famennian extinction events,^[2] which it is unlikely to have affected.

• http://en.wikipedia.org/wiki/Alamo bolide impact