Found: The closest I got was a page stating that a 100-g golf ball or stone striking the temple "with medium force" can be fatal.
Scenario: I want to kill a character with quick blunt force to the temple--I'm looking at about 80-100 grams striking the character's temple with no warning. The mass can be greater, but not drastically. It will be a man, Mediterranean descent, fairly healthy, in his forties to fifties. He's a minor character, and so I can kill him off in other ways (as long as he dies), but now I'm highly curious about this one.
How much force would be required to fatally fracture this man's temple?