Palynostratigraphy and palaeoecology of the Niur Formation, Tikdar section, northwest of Kerman, Central Iran

Abstract Diverse, moderately to well-preserved palynomorphs including acritarchs (sensu stricto), prasinophytes cyst, chitinozoans, scolecodonts, and spores occur in some surface samples (90 meters thereof) of the Niur Formation (200 m thick) at the Tikdar stratigraphic section, northern Kerman, Central Iran. The palynofloras embrace one species of prasinophyte cyst, 25 species (assigned to 14 genera) of acritarchs, 8 species (attributed to 6 genera) of chitinozoans, and 2 species (assigned to 2 genera) of spores. Based on the stratigraphic distribution pattern of acritarchs (sensu lato) one local assemblage zone (Evittia denticulata denticulata - Lophosphaeridium papillatum-Eupoikilofusa striatifera assemblage zone) is introduced in the strata investigated herein. The known stratigraphic importance of such acritarchs and chitinozoans as Eupoikilofusa striatifera, Geron amabilis, Spinachitina fragilis and Ancyrochitina convexa as well as the lack of Middle and Late Silurian index taxa allow for the host strata to be attributed to the Early Silurian (Llandovery). Notable abundance of transparent AOM in majority of the samples (except those labeled as 318–326 and collected 38–88 above the base) examined indicates sedimentation in a marginal marine setting with relatively low oxygen level. Such palynofacies data as proportion of blade-shaped to equidimensional opaque palynomacerals and AOM/marine palynomorphs ratio in the material studied tend to support such generalizations on the depositional environment. Keywords: Palynostratigraphy, Marine Palynomorphs, Palaeoecology, Niur Formation, Central Iran. Introduction The geographic distribution outline of sediment and extensive emergence in Iran during Silurian tend to support the hypothesis relating such events to the Caledonian epirogeny. The Silurian deposits are so far reported from eastern Alborz Ranges, Central Iran, and southeastern Zagros. Nabavi (1976) believed that because of the Caledonian movements, vast areas in north and northwest of Iran emerged while in east and northeast of the country marginal marine deposition continued; boundary between the two is speculated to be along a line extending from Aliabad (east of Gorgan) in the north through Semnan to Zardkuh (Zagros Mountains) in the south. Another significant characteristic of the Silurian in Iran is the presence of basic submarine volcanic rocks (basalts) reported from many areas indicating a rift in the otherwise coherent Paleozoic cratonic