The oldest rocks in the Southern Meyaneh basin area are a series of “metasediments,” dolomites, and quartzites probably Late Devonian in age, on top of which occur 126 meters of dolomitic limestone which contain well preserved productoid brachiopods of Carboniferous age.
No Permian or Triassic rocks have been recognized in the area, but the Jurassic is represented by coal-bearing, gray, silty to argillaceous sandstones of Liassic age called the “Ghaleh Bulagh” Formation. Above these sandstones are 120 meters of a sandstone-limestone sequence of Sequanian to Lower Tithonian age, which the writer has called the “Ouzeh” Formation. No sediments of Cretaceous age have been found.
Except for the Paleocene, the Tertiary is fairly complete in the area of investigation, and there is evidence of sporadic volcanic activity from Eocene to Early Miocene time. The only marine sequence in the area is about 270 meters of alternating calcareous shale and organodetrital reef limestone, the Marine member of the Qum Formation of Oligo-Miocene age. The Qum Formation is conformably overlain by 2,700 meters of continental redbeds known as the “Upper Red” Formation. Pliocene deposits exposed in the eastern part of the area are composed of a basal conglomerate and a sequence of light yellow to pinkish silts and clays.
Structurally the area consists of three provinces. 1. The broad homocline at the south forms the southern plateau and dips northward into the basin. 2. A domal structure west of Mushampa is a sharp semi-elliptical upwarp containing a few subsidiary structures. Several faults are present in this province radiating from the core of the dome. 3. The north and central part of the basin is tightly folded and faulted by intense deformation of incompetent “Upper Red” deposits.