Facies, Depositional Environment and Sequence Stratigraphy of the Mobarak Formation in Jeyrud Area (North of Tehran)

Category Sedimentology
Group GSI.IR
Location 23th symposium on geosciences
Holding Date 05 May 2008

      The Mobark Formation (Lower Carboniferous) in Jeyrud area (north of Tehran) is overlain and underlain with disconformable contacts, by Dozdband and Jeyrud Formations respectively. The thickness of the Mobarak Formation in Jeyrad area is 322 meters and is divided into Member 1 and 2.
   These Members consist of various facies related to fairweather conditions, but facies related to storm and turbidity currents are also recognized. These facics, based on their depositional environment, belong to four facies groups related to open marine, barrier, lagoon and tidal flat sub-environments.
   Facies of Member 1 related to open marine, bioclastic barrier and lagoonal sub- environments. Open marine facies, particulary the dark grey shales of the deeper part of this environment , make the main part of Member 1. Storm and turbidity current deposits are recognized in this Member. The carbonate turbidites indicate that Member 1 was deposited in a distally steepened ramp during sea-level highstand, similar to the deep (off bank) of the present day bahamas platform.
   Facies of Member 2 belong to open marine,bioclast/ooid barriers, Lagoon and tidal flat sub-environments. Preservation of the ooids indicate high global sea-level and formation of low Mg calcite ooids. Rocks of Member 2 were deposited in a carbonate ramp similar to the southern part of the Persian Gulf.
   Field and microscopic studies of the Mobarak Formation have led to recognition of seven sequence (3rd order cycle) and several small scale shallowing upward cycles (parasequence). Member 1 consists of three sequences and Member 2 contains four sequences respectively. The lower contact of sequence 1 with Jeyrud Formation, contact between sequence 3 and 4 and the upper contact of sequence 7 with Dozdband Formation are type 1 unconformity (SB1) and other contacts are type 2 unconformity (SB2). These sequences belong to the upper part of Kaskaskia supersequence.

tags: TEHRAN