Biostratigraphy of Devonian-Carboniferous boundary in Tuyeh-Darvar section, north of Iran

Devonian-carboniferous boundary is not clear in the eastern alborz mountains. in the current study tuyeh-darvar section with about 170 m, thickness is selected. in this investigation, the primary goal is revision of devonian/carboniferous boundary (known as dcb) and the other goal is the redefinition of the dcb as a famous necessity (based on ics program in 2008 for defining the boundary and to find a new gssp). according to conodont data from acid-leaching 53 carbonate samples(by acid acetic) that obtained from late devonian and early carboniferous deposits in this section, and based on standard conodont zonation 6 zone are recognized; 1. bi.ultimus/or si.praesulcata zone, 2. pr.kockeli /or si.sulcata zone, 3. si.duplicata to si.sandbergi bio interval, 4. si.crenulata zone, 5.gnathodus-p.inornatus zone, and 6.ps.multistriatus zone. considering to the conodont zones above mentioned, conodont faunas and other evidences, in the tuyeh-darvare section the dcb, is located within cream to grey silt stone beds, which are lies between k_6 limestone and k_8 dark carbonate beds (about 7.10 m above the base of recent studied section).