Mid-Cretaceous radiolarian faunas from the Ashin Ophiolite (western Central-East Iranian Microcontinent)

The Ashin ophiolitic melange crops out in the west of the Central-East Iranian Microcontinent (CEIM). Accurate dating the deep-water radiolarian chert deposits associated with this ophiolite provide valuable data to constrain the stratigraphic and paleotectonic evolution this Neo-Tethyan oceanic basin. Chert nodules within Upper Cretaceous limestones and chert layers overlying pillow lavas of this ophiolite were collected and examined in detail for the first time. Radiolarians indicate that the cherts accumulated in the mid-Cretaceous in a deep marine setting within the eastern branch of the Tethyan Ocean in Iran. Two distinct radiolarian faunas, one mid-Albian (∼107 Ma) the other Turonian (∼94 Ma) were recovered. The radiolarian microfossil ages are consistent with radiometric ages previously obtained from associated plagiogranites and quartz keratophyre. This study indicates that mid-Cretaceous radiolarian assemblages from the western CEIM are similar to other radiolarian faunas reported from Cretaceous ophiolites in Greece, Turkey, Iran (Outer Zagros Ophiolitic Belt in Iran, e.g. Khoy, Kermanshah, Neyriz, and Soulabest), and southern Tibet in China.