Palynostratigraphy and Paleogeoraphy of Lower Paleozoic Strata at Kuh-e-Boghou، Southwest of Kashmar City، at Eastern Central Iran

Acritarchs from the Shirgesht, Ghelli and Niur formations were used to determine the age of these rock units and to assess their paleogeographic importance. These formations yielded 55 palynomorph taxa (54 acritarch species and 1 cryptospore species) permitting the recognition of eight biozones (palynozones). The zones I - III represent the Early Ordovician (Tremadocian-Arenigian), zones IV-VI indicate Middle-Late Ordovician (Llanvirian-Ashgillian) and zone VII suggests the Early-Middle Silurian (Llandoverian- early Wenlockian). The presence of genera such as Arbusculidium, Striatotheca and Coryphidium in the Early Ordovician sediments of the Shirgesht Formation from the eastern Central Iran suggest, that the Iranian Platform was part of Peri-Gondwanan Paleo-continent, possibly along the southern shore of the Paleo- Tethys Ocean during the Early Ordovician. Comparison of acritarch taxa from the Ghelli (Middle-Late Ordovician) and Niur (Early-Middle Silurian) formations with those from other parts of the world indicate broad similarity with those of the United States, Europe, North Africa and China. This similarity suggests that the Peri-Gondwanan Paleo-continent began moving northward during the Middle-Late Ordovician and by the Silurian formed part of the supercontinent Pangea. The diverse palynomorph taxa (acritarchs, chitinozoans and scolecodonts) in the Early Ordovician (Shirgesht Formation), Middle-Late Ordovician (Ghelli Formation) and Early-Middle Silurian (Niur Formation) strata indicate a marine depositional environment.