Middle-Late Cambrian acritarchs from the Zardkuh area in the High Zagros Mountains, southern Iran: Stratigraphic and paleogeographic implications

The excellent preservation of the acritarchs, their great abundance, diversity andgood stratigraphic control permit establishment of a detailed middle and late cambrianacritarch biozonation. a total of 56 palynomorph species form the basis of 10 localacritarch assemblage zones. assemblage zones i-ii occur in the lower and middle partsof the member c of the mila formation and suggest early-mid middle cambrian;assemblages zones iii-iv appears in the upper part of the member c of the milaformation and the lower part of ilebeyk formation and encompass latest middle andearliest late cambrian; acritarch assemblage zones v-ix occur in the middle and upperparts of the ilebeyk formation and characterize late cambrian; finally, acritarchassemblage zone x appears in the basal part of the zardkuh formation and proves tohave an early tremadocian age. amongst the late cambrian acritarch assemblages oflaurentia only the two cosmopolitan species of timofeevia phosphoritica andvulcanisphaera turbata are shared with coeval strata in the high zagros mountains.iranian acritarch assemblages show a marked gondwanan paleobiogeographicalaffinity, share a high proportion of taxa with typical baltican and north africa–gondwanan assemblages, and are different from known laurentian microphytoplanktonsuites. these results are in general agreement with paleogeographical models that placeavalonia, baltica, and the north african part of gondwana, at relatively high southernpaleolatitudes, whereas laurentia occupies a sub-equatorial position. four new acritarchspecies, namely leiosphaeridia iranense, navifusa reticulata, ooidium zagrosensis, andveryhachium ilebeykensis are described.