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

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.