Paleontological Modification of Carboniferous Deposits at Simeh-Kuh Section - Northern Damghan, by Four Conodont Biozones

During the Carboniferous time, Iran was a part of the northern margin of Gondwana. Carboniferous deposits of Iran are characterized by continental to shallow marine deposits. The studied section (Simeh- Kooh) is located in 5 Km Northwest of Damghan city in the east Alborz region. The lower Carboniferous Mobarak Formation consists of variable thickness of limestones interbeded with shale beds. The thickness of this section is about 115 m. The Mobarak Formation overlay the upper Devonian Jeirud Formation with a transitional contact and is unconformably underlain by lower Permian mixed siliciclastic-carbonate succession of Dorud Formation. This research is focused on the conodonts and facies. Conodont elements consist of 13 genus and 19 species. 5 Biozones is identified including, costatus zone (Latest Famennian), Sandbergi-L. crenulata zone, isostaticha-U. crenulata zone (Middle Tournaisian), typicus-anchoralis-latus zone (Late Tournaisian) and G. bilineatus zone (Middle-Late Visean) correspond to global zonation. The Tournaisian succession consist of alternation of organic matter rich shales and dark thin-bedded limestones is supposed to have deposited in a deep marine environment with a low oxygen condition. The paleontological and facies characteristics of Devonian-Carboniferous transition definitely show a rapid sea level rise and flooding event in this time in Eastern Alborz which corresponds with the Hangenberg Bioevent known in other parts of the world.