Document Type : Original Research Paper


1 Geology Department, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran. Geology Department, Faculty of Sciences, Shahid Bahonar University, Kerman, Iran

2 Geology Department, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran.

3 Geology Department, Faculty of Sciences, Birjand University, Birjand, Iran


The Lower Cretaceous sedimentary succession of western Kopet Dagh Basin (Sarcheshmeh and Sanganeh formations) was investigated. Taking into account the considerable thickness of the studied section (1668 m) and the possibility of recording all the important events, determination of calcareous nannofossil biostratigraphy was put on the agenda. This resulted in recognition of NC5, NC6 and NC7A nannofossil zones. Accordingly the age of the Sarcheshmeh Formation within the studied section is determined as Late Barremian- Early Aptian while the age of the Sanganeh Formation is late Early Aptian- early Late Aptian.  The calcareous nannofossil assemblage of Sarcheshmeh and Sanganeh Formations has a Tethyan affinity with abundant warm-water varieties such as Rhagodiscus spp. and Nannoconus spp. while the cold-water species like Repagulumparvidentatum and Seribiscutum spp. are rare.


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