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The Lower Carboniferous carbonates of Mobarak Formation is studied on a flank of the Ozoom Anticline 22 Km. Northeast of the town of Jajarm, where the formation conformably overlies the Devonian Khoshyeylagh Formation and is overlain disconformably by the Permian continental clastics. The Mobarak Formation is a rather persistent rock unit in the east and central parts of Alborz Range.
A detailed Petrographic study of 290 vertically oriented thin section revealed that the formation consists of 4 distinct sedimentary units as follows:
1-A basal conglomeratic unit indicating sea transgration.
2-A low energy subtidal unit which changes to a high energy environment towards the top.
3-A stromatolitic dolomite belonging to an intertidal environment.
4-A brecciated dolomite with some pseudomorphs of gypsum and anhydrite indicating supratidal environment.
In the previous description of the Mobarak Formation in the Kuh- e Ozoom by Afshar Harb (1979) a 2 meter siltstone bed represents the basal part of the formation. Regarding to the lithological similarity with the underlying beds this bed is excluded from the Mobarak Fm.
The above mentioned carbonate units appear to be the ancient equivalent to Mobarak shallowing- upwards sequence. Such a comparison therefore confirms that the above mentioned basal siltstone unit is not a part of the Mobarak carbonate body.