The Scanlan, or Midway, dome is 14 miles south of west of Hattiesburg, in Lamar County, Mississippi. The approximate center of the dome is in Sec. 28, T. 4 N., R.15 W. It is 110 miles northeast of the Sorrento dome in Ascension Parish, Louisiana, the closest producing coastal salt dome. The only other salt dome discovered to date in Mississippi is 96 miles northwest of the Midway dome, in western Hinds County.

Early interest in the area resulted from subsurface correlation between widely separated dry holes. Core drilling and test wells have revealed a domed structure elongate northeast and southwest with several hundred feet of closure. Several wells have found anhydrite and salt.

The Midway dome is a geological prospect. The stratigraphic section of the Eocene does not differ much from that normal for the area unless it is in the scarcity of sand bodies of any consequence. Structurally this is a piercement-type dome, belonging, in the writer's opinion, in the inland rather than the coastal classification. Salt movement had its maximum development in late Tuscaloosa or pre-Eutaw time, but continued until late Oligocene time. The oil accumulation that resulted in the asphaltic sand took place prior to the close of Tuscaloosa time.