The pilot was making a personal cross-country flight under Title 14, CFR Part 91. He said he was circling an off airport landing site at a reduced power setting, and when he applied throttle the engine quit. The pilot reported that during taxi for takeoff prior to the flight, the airplane's engine had carburetor ice, and he felt that this was what caused the engine to quit since he had not applied carburetor heat when he reduced power. The airplane made an emergency descent and impacted on muskeg. During the landing, the main landing gear attachments and left wing were damaged. The pilot indicated that there were no known mechanical problems with the airplane prior to the accident.