Steamboat Butte and Pilot Butte anticlines are large, asymmetric folds bounded by east-dipping reverse faults that root in Precambrian basement. Displacement on the bounding faults is approximately 1,500 ft (457m). Reverse faults of lesser displacement parallel the major fault. An unusual out-of-the-syncline, east-dipping thrust fault exists on the northeast flank of Pilot Butte anticline. A major, down-to-the-west normal fault on the west flank of Steamboat Butte anticline postdates the Eocene Wind River Formation. No other major normal fault is known in this area. Production of hydrocarbons is limited to the hanging wall of the major reverse fault.