The pilot was taking off from a gravel airstrip in a tailwheel-equipped airplane. During the takeoff roll, the pilot said that the airplane began to veer to the left despite his attempts to correct with right rudder. He decreased the engine power, but the left wheel caught a berm, and the airplane ground looped, sustaining substantial damage to the left wing. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.