Conodont biostratigraphy and biofacies of Late Devonian-Early Carboniferous deposits at Chelcheli section, Northwest Shahrud (Eastern Alborz)

Chelcheli section (397m thick) about 70 km northwest of Shahroud on the Shahroud-Gorgan road (Tuskistan route), about 5 km east of the Chahar-Bagh village is sampled and studied  to investigate the DC transition and the conodont facies changes during the Global Hangenberg Crisis. The measurement of one hundred eighty two meters of the upper part of Khoshyilagh formation and 215 meters of the Lowermost Mobarak formation  led to the discrimination of 11 rock units with different sedimentary features.  In total, forty limestone samples, about 4-5 kgs were systematically collected and treated with conventional preparation methods. Three hundred forty  conodont elements were obtained, which led to the identification of 47 species and subspecies belonging to 16 genera that allowed the separation of 15 conodont bio-zones from the early Famennian to the Late Tournasian.