Writers : Sohrabi, Sima; supervisor: S. Feiznia;advisor: A. Sadeghi, H. Torshizian
Refference : M.Sc.Thesis _ Shahid Beheshti university, Tehran;185p.
Publishing Year : 1378

Abstract :

The Kopet - Dagh sedimentary basin in eastern north of Iran has fault contactwith Tooran platform from the north and is bounded to the south by Binaloo )mountains . According to Berberian and King (1981), this zo ne
becomes sediments basin after early Kimmerian orogenic event (It happened when the concurrence of Iran and Tooran finished) and thick sediments were gathered with various facies from Jurassic to Miocene without important stratigraphic gap. These sediments were deformed under late Alpine orogenic events and formed various anticlines and synclines with northwest - southwest strike
The main aim of this research is to view sedimentary environment of Tirgan formation in central part of Kopet - Dagh basin.
Type section of Tirgan fo rmation in the 40th kilometer of Dargaz is 780. thick meters thick with the age of Neocomian - Aption

The thickness of this formation in the 40 meters in the east of Kopet - Dagh basin in Mozdooran. The contact of these two formations (Shoorigeh and Sarcheshmeh) is sharp.
In some part pf Kopet - Dagh sedimentary basin, Tirgan formation is as reservoire rock of gas resources in the north of iran. Mozdooran and Tirgan formation are also counted as kartsic formation in Kopet - Dagh basin and are valuable regarding to water resources. (from the Point of water resources)
In this research, Tirgan formation was studied in Radkan and Dadanloo (the thickness of 257 and 387 meters) in detailed
3.5 150 hard samples and JO soft samples were taken with average distance Of4 meters and thin sections were taken from hard samples. Detailed Petrographic studies ,resulted in distinction of 13 microfacies

They are as follows: 1- Calcimudstone . 2- Bioclastic wackstone. 3- Bioclastic packstone 4- Oncolithicpackstone 5- Oolitihc grainstone 6- Oolithic bioclastic> packstone 7- Mixed grainstone 8- Mixed packstone 9- Peletoid grainston< 10- Aggregate packstone 11- Aggregate grainstone 12- Sandstone 13- Marl.
On the bases of fossils contents and their vertical position in stratigraphic sectione. It was recognised that Microfacies 1,2 and 3 belong to open? marine and lagoon and were placed (settled) in facies belt 2 and 7 of Wilson.
Microfacies 4 belong to facies on belt 6 of Wilson which is located between Oolithic bar and open marin.
Microfa 5 and 6 belonged to facies belt 6 of Wilson show bar and beach.
Microfacies 7 and 8 belong to facies belt 7 and 8 of Wilson (1975)
Microfacies 9 were formed in Radkan section which were in facies belt 8 of

Microfacies 10 and 11 were seen in Dadanloo section which belonged facies belt8 of Wilson.
Generally, sedimentation of Tirgan formation were formed in Tidal flai supradital intertidal) and subtidal environments. This basin was deepended with the passage of time so that shaly and Marly sediments of Sarcheshmeh formation were placed over Tirgan formation conformably and with variation of facies change inic open marine environment.
According to these results, horizontal model of deposition of Tirgan formation was drown.
Features,processes and important diageneric environments in Tirgan formation are as follow: Micritization, Bioturbation, Geopetalfabric, Isopaques fibrous rim cements and early dolomitization were distinguished in marine pheriatic. Earl compaction Aragonitic shells winnowing were formed is under saturated fresh, water pheriatic zone.

Filling cavity and fractures by spary cemen forming syntexial overgrowth drucy cement, Poikilolopic cement and Neomorphism happened in active saturated fresl water pheria zone.
Meniccus, pendent cement and vadose sitl were formed in fresh water vados zone.
Late compaction, stilolitation, late dolomitazion (Saddle dolomite)
formation of Authigenic minerals and late fracture filling happened in burial environment. Cathodolominecence analyses, Electrone Microprob analyses were done in some thin sections. Catodolominecance analyses demonstrated that cementation was occured in different phases. Fibrous cement deposited in environment.
For more detailed studies of diagenes marine and evestigation of environment of dolomite formation. Isotopic investigation, Electromacroprop anlysis, SEM and cathodolominecance studies are needed But according to Petrographic documents and staining by Alizarine red s and Potacium ferrocianore we can conclude that dolomization in this formation in intertidal region lagoon region and also bar region which probably was the result of mechanism of reflux and seepage and dolomitization in burial diagenesis.

Subject List : Depositional environment, Microfacies