Significance of Tornacia sarjeantii in palynostratigraphy of the Upper Devonian strata, west of Garmabdar, northeast Tehran

Diverse and well preserved palynoflora dominated by organic-walled marine microphytoplankton (acritarchs and prasinophyte phycomata) and radiosymmetrical spores together with scolecodonts, cryptospores, and chitinozoans occurs in surface samples of the Geirud Formation at the Garmabdar section, northeast Tehran. Palynotaxa such as Daillydium pentaster, Gorgonisphaeridium ohioense, Papulogabata annulata, P. lobata, Cymatiosphaera perimembrana, C. radiosepta, Chomotriletes vedugensis, Deltotosoma intonsum, Crassiangulina tesselita, Tornacia sarjeantii, Unellium lunatum, U. piriforme, and Retispora lepidophyta appear to have well known Late Devonian (Frasnian-Famennian) vertical ranges. Of these, index taxa such as G. ohioense, D. pentaster, U. lunatum, U. piriforme, and T. sarjeantii are extensively used in dating and long-distance correlation of the Devonian strata. Tornacia sarjeantii range biozone (Frasnian-Famennian in age and 118m thick) is introduced herein on the basis of first and last observed occurrences (FOO and LOO) of the eponymous species and compared with local microphytoplankton-based biozones previously established in virtually equivalent sequences elsewhere.