Lockne crater Wikipedia
Lockne is a meteorite crater, located approximately 21 km (13 mi) south of the city of Östersund in northern Sweden. It has been suggested that it is a doublet with the nearby smaller Malingen Crater, 16 km apart. Computer simulations suggest that the asteroid that created the Lockne crater was some 600 meters in diameter, and the one that carved out Malingen crater was about 250 meters across.
It is 7.5 km in diameter and the age is estimated, based on accompanying chitinozoan microfossils, to be 458 million years (Late Ordovician). The crater is exposed at the surface. Its fossils, typical of shallow marine environments, show it to be a marine target impact event.