Lukas Marxt’s fourth film about the Salton Sea in Southern California focuses on 1944/45, when about 150 dummies, replicas of the bombs of Hiroshima and Nagasaki, were dropped there for ballistic tests. “Marine Target” measures the remains of the wooden target platforms from up close and high above. The disconcerting soundtrack to this fascinating filmic study is provided by a swelling adaptation of the Nigerian hit “Atomic Bomb” by William Onyeabor.