The pilot stated that upon returning to the airport from a local flight, he elected to land on the grass turf runway, which had an asphalt runway intersection within the first quarter of its length. His landing speed was about 60 mph, the airplane touched down long on the first portion of the grass turf. The pilot held off lowering the tail wheel initially but then lowered it firmly onto the ground. During the landing roll on the asphalt portion, the airplane began to arc to the left, the pilot applied full right rudder and then eased on a “slight amount” of right brake. As the airplane departed the asphalt section, it abruptly nosed over, the propeller struck the ground and the airplane came to rest inverted on the grass turf runway, incurring substantial damage to the vertical section and rudder. An inspection of the runway’s asphalt to grass turf transition section revealed that the airplane’s main landing gear tires dug into the turf as it left the slightly higher asphalt. No preimpact mechanical malfunctions or failures with the airplane were noted that would have precluded normal operation.