Writers : Reissadat,Naser;Moussavi Harami;Seid Reza
Refference : Geoscience Scientific Quartarly Journal,No.7
Publishing Year : 1372

Abstract :

The Kopet_ Dagh basin of north and northeast Iran was a site of continuous sedimentation from Jurassic through Tertiary. The area of study is located in eastern part of the Kopet_Dagh basin in northern flank of a Plunging anticline. For the purpose of this study, two stratigraphic sections were measured in ditches east of Mashhad - Sarakhs road and south of Baghak Village. The Sarcheshmeh Formation, in the study area, conformably overlaie the Tirgan Formation and underlain the Sanganeh Formationand can be divided into lower (marly) and upper (shaly) parts. The lower part consists of interbedded marly limestone, marl and fossiliferous oolitic limestones and the upper part is composed of gray shale with fossiliferous limestone. The Sanganeh Formation consists of dark colored clayey shale that gradually changes upward to silty-shale and siltstone.The presence of glauconite within the shale of the upper part of this formation, gives it an olive green colour.
In this study, one biozone and three subzones were identified for the Sarcheshmeh Formation. In ascending order those are: Orbitolina Kurdica_ discoidea zone that has been divided into Nautiloculina oolitica, Nautiloculina oolitica _ pseudocyclamla sp., and pseudocyclomia sp. Two biozones of Lenticulina osnabrugensis and Tritaxia macfadyeni were identified in the Sanganeh Formation. Lenticulina osnabrugensis zone has been divided into Marsonella trochus, Globorotalites Cf. brotzeni and Dorothie bullate. Based on biozonation and identified fossil assemblages in this area, the age of Aptian for the Sarcheshmeh and Albian for the Sanganeh Formation have been suggested. Study of fossil assemblages also indicate that during deposition of these assemblages , a very shallow marine environments with gradual increases in depth was present in the study area.

Subject List : stratigraphy