Ostracoda of the Abderaz Formation in the Mozduran Section, East Kopet-Dagh

The Kopet-Dagh Depositional Basin has hosted a site for deposition of Jurassic to Miocene which well exposed in parts of Turkmenistan, north of Afghanistan and the northeast of Iran (Aghanabati, 2004). One of the most prominent Formations of the Upper Cretaceous in the Kopet-Dagh Basin is the Abderaz Formation. The main lithology of this formation includes shale and marls with three horizons of chalky limestone. The aim of this study is to determine ostracoda, from Abderaz Formation in Mozduran section.

A total of 102 samples of the Abderaz Formation in the east of the Kopet-Dagh Basin were collected. Samples were soaked in a mixture of water and 15% hydrogen peroxide. The content of each bucket was washed up and passed through sieves of 30 and 80-mesh.The sieves had been topped on each another regarding the grain size from course to fine. The samples were, then, dried off and transferred onto standard cans. The ostracoda, themselves, were separated from the rest of sediments through a brush and stored in some slides. Sticking the samples on the stubs, and covered by a film of gold. Then all of samples were photographed and studied.

Ostracoda are one of group of fossils that are index for reconstruction of environmental conditions. Due to the higher sensitivity to environmental changes, so are local. This leads to a lack of global standard biozonation for them. Not with standing this fact, the Ostracodas have saved their own biostratigraphy validity. In the studied samples, all specimens from the Abderaz Formation in Mozduran section are well preserved. In the studied section, 16 genera, and 40 species of the ostracoda were identified. The studied interval spans the 4 ostracoda biozones. In this research in addition to the investigation of ostracoda, calcareous nannofossils have been studies too, and compared. Ostracoda biozones and results of the comparison with calcareous nannofossils are as follow:1- Rehacythereis sp. Interval Zone
This biozone is virtually equivalent to the biozone of Calculites obscurus (CC17) and Aspidolitus parcus parcus (CC18) of Sissingh (1977).
2- Haplocytheridea sp. Interval Zone
This biozone is virtually equivalent to the biozone of Calculithes ovalis (CC19) of Sissingh (1977).
3- Veenia sp. Interval Zone
This biozone is virtually equivalent to the biozone of Ceratolithoides aculeus (CC20) of Sissingh (1977).
4- Cytherellaida sp. 5 Range Zone
This biozone is virtually equivalent to the biozone of Uniplanarius sissinghii (CC21) of Sissingh (1977).
Based on the identified calcareous nannofossils and ostracoda, the age of the Abderaz Formation in Mozduran section is Late Santonian to Early late Campanian.