The effect of the sub-Hercynian phase in the east of Kopet ? Dagh Basin (North and north ? east of Mashhad)

Category Paleontology and Stratigraphy
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 24 May 2008

      The sub- Hercynian phase coinciding with the end of Cenomanian is one of the Alpain cycle phases. This tectonic phase caused orogenic and epirogenic movements, Facies changes and volcanic activities in different parts of Iran. Kopet ? Dagh Basin in north ?east of Iran with a thickness of more than 6000 m of sediments , were accumulated during Triassic ? Miocene periods. This basin has been affected by sub ? Hercynian tectonic phase during cenomanian ? Turonian.
   In order to study, the effect of this phase in kopet ? Dagh region, two stratigraphic sections, one in Mozduran type section and the other in Taherabad Village, were selected and studied within the boundary of Aitamir and Abderaz Formations in the eastern part of this basin.
   In this study 40 species belonging to 32 genuses of foraminifera and 3 species of non-foraminifera were recognized. Based on the fossil assemblages on the top of Aitamir Formation such as Rotalipora cushmani, Rotalipora appenninica , Rotalipora deeckei near the end of cenomanian age is suggested for the top of this formation.
   Fossil assemblages in the base of Abderaz formation such as Helvetoglobotruncana helvetica and marginotruncana renzi indicates early parts of Middle Turonian age for the base of this formation.
   Therefore, in this part of Kopet ? Dagh Basin, between near the end of Cenomanian and early parts of Middle turonian a hiatus is resulted by sub ? Hercynian movements.