Fault-bounded basins containing several thousand feet of sedimentary and volcanic rock of Cenozoic age are indicated by gravity lows in the Oakley area and in Upper-Raft River and Raft River Valleys. A gravity low and a magnetic high in the north end of Raft River Valley extends over the Cotterel Mountains and into Marsh Creek valley. These anomalies may reflect a Tertiary caldera. A gravity high and a magnetic high in the Raft River Valley south of Malta suggests a buried intrusive that may be the source of heat for the thermal waters in that area.