My father told me about a short story he read many years ago about a man in the military getting transported back in time to viking age Greenland by an atomic bomb. He was taken in by the vikings. He defended the village from a raid and was buried with all viking honors in a cliff. In the modern time, the archaeologists unearthed him and realised that he must have been a time traveler, because he was buried in his clothes with his firearms, as well as having his history carved into the stone.
Can anyone help me identify this story?