Open Journal of Geology, 2013, 3, 178-186 doi:10.4236/ojg.2013.33021 Published Online July 2013 (http://www.scirp.org/journal/ojg) Investigation of the Boundary between Abderaz and Kalat Formations Based on Calcareous Nannofossils in West Kopet-Dagh (NE IRAN) Mohammad Anvar Moheghy * , Fatemeh Hadavi, Behname Rahimi Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran Email: * moheghy@gmail.com Received February 26, 2013; revised March 26, 2013; accepted April 26, 2013 Copyright © 2013 Mohammad Anvar Moheghy et al. This is an open access article distributed under the Creative Commons Attribu- tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT The biostratigraphy of calcareous nannofossils of the Cretaceous is investigated in the boundary between Abderaz and Kalat Formations through the record of species richness, diversity and distribution patterns in the west Kopet-Dagh re- gion. The Kalat Formation comprising of coarse-grained detritus limestone with subordinate sandstone intercalations and the Abderaz Formation mainly consists of limestone, Shale and Limy marl. Nannofossils of this boundary in each of studied sections are listed and figured. 21 species in Ghalehzoo section, 29 species in Sheikh section and 19 species in Jozak section have been determined. Boistratigraphy based on calcareous nannofossil allow the identification of nannofossil standard zones CC21 and CC26 in all of sections, According to these zones in all of sections, the age of the studied thickness is Early Late Campanian-Late Late Maastrichtian in these sections. Keywords: Nannofossils; Biostratigraphy; Abderaz; Kalat; Iran; Kopet Dagh 1. Introduction The investigation of calcareous nannofossil assemblages from the boundary of Aberaz and Kalat Formations al- lowed for the testing of nannofossil biozonation schemes and will be used to document the biostratigraphical changes throughout the late Cretaceous of the Kopet Dagh basin. The sediments are preserved and including several species recently described from the upper boundary of Abderaz Formation and lower boundary of Kalat Forma- tion in west Kopet Dagh that have not been recorded previously from these regions (Figure 1). The aim of this study is to provide a catalogue of the species encountered in this boundary to serve as a guide for future studies in this area. 2. Geological Setting Kopet Dagh has a complete Cretaceous sedimentary suc- cession comprising marine shales, marly limestone and subordinate sandstones. This sequence seems to represent all stages of the Cretaceous [1,2]. The Abderaz Formation is composed of light gray to grayish white shale and three to four chalky limestone beds. Abderaz Formation is exposed in vast area in Kopet- Doghrange. An indication of thickness increases of Ab- deraz Formation in the eastern Kopet-Dogh from 500 m in the southern (Shurijeh) to 1500 m in the northest (Ta- herabad) [1]. The Kalat Formation is a unit of limestone contains subordinate sandstones intercalation and is conformably interbedded between the Abderaz Formation below and Nafteh Formation above. Thicknesses of this formation decrease from east to west of Kopet Dagh [3]. As it is shown in Figure 2, four biozones of CC22- CC25 are missed in all three sections the reason for that could possibly be related to the disconformity between Kalat and Abderaz formations. According to the Stocklin 1968, the Abderaz formation is overlaid by Abtalkh and this formation is covered by Neyzar formation in the east of Kopet-Dagh, as all these two formations are missed in these three studied sections. We can conclude that the contact between Abderaz and Kalat formations would be unconformable as discussed previously by Afshar-Harb * Corresponding author. Copyright © 2013 SciRes. OJG