Palynomorphs and Plant macrofossils Biostratigraphy of the Calshaneh area, NW Tabas: Paleoclimate and paleogeography analysis

Hojedk Formation well exposed in the Calshaneh area, northwestern of the Tabas city, Central-East Iran. Here, I documented one section and Core No 4. Its palynomorphs introduced for the first time. The host strata span the Aalenian-Bajocian and contain moderately to week preserved palynomorph species in which four spore species (4 genera), nine pollen species (6 genera), and nine dinocysts (4 genera) are recognized. Vertical distribution of palynomorphs allows erection within the Hojedk Formation of one miospore biozone-Klukisporites variegatus-Callialasporites dampieri Assemblage Zone- and one distinctive dinocyst biozone- Pareodinia ceratophora-Nannoceratopsis gracilis Assemblage zone. These biozones compared with palynozones from ±coeval strata in Iran and elsewhere especially in Northern hemisphere. Therefore, it can conclude that Calshaneh area located at the coastal boundary of Iran, along the Tethys Ocean. Moreover, Hojedk Formation contains plant macrofossils belonging to 17 species allocated to 11 genera of various orders. One biozone-Nilssonia sp. cf. N. bozorga-Klukia exilis Assemblage Zone- recognized in the Hojedk Formation at Calshaneh section. According to occurrence of Klukia exilis and Coniopteris hymenophylloides, a Middle Jurassic age suggested for this assemblage. Furthermore, relative abundances of taxa studied and relative abundances of order Nilssoniales, Ginkgoales, Filicales, and Equisetales were 44.44%, 20.64%, 15.87, and 7.94% respectively. It is noteworthy that variety and relative abundance of the species of Genus Nilssonia (6 species, 42.27%) and species of Order Ginkgoales (2 taxa, 17.46%), as a macrophyllous cycadophyte, was high within the Calshaneh area. Therefore, a humid subtropical to temperate climate considered for this period in this area.