new data on the frasnian/famennian boundary in kal-e-sardar section, eastern tabas (central iran)

frasnian - famennian boundary in the kal-e-sardar section (east of tabas, central iran) is investigated on the basis of conodonts. distribution of thirty-three species and subspecies in the stratigraphic column enables us to recognize a barren interval and five biozones; upper rhenana, upper part of upper rhenana - linguiformis, lower to middle triangularis, upper triangularis, lower crepida. biofacies analysis shows a deepening trend through the late frasnian and then a sharp sea level fall present at the base of early famennian sequences. deeper environment governs through the famennian stage. a new range is proposed for p. planarius; lower hassi - linguiformis zones.