Palynofacies analysis and paleoenvironmental interpretation of the Dalichai Formation, northeast of Semnan

Palynological and Palynofacies analysis combined with sedimentological studies have been performed on Dalichai Formation, northeast of Semnan, in order to define its paleoenviromental interpretation. Based on petrographic studies of organic matter, three palynofacies types were recognized as PF1, PF2, and PF3. PF1 is a characteristic of proximal shelf settings or basin. This palynofacies in the lower part of Dalichai Formation represents the shallowest environment because it is comprised almost exclusively of large black phytoclast while PF1 in limestone successions in the upper part of Dalichai Formation was deposited in distal setting under suboxic environment. This interpretation is supported by sedimentological and paleontological data. PF2 represents the lower and middle parts of the formation with high contents of brown wood and sporomorphs. In addition, it shows the presence of fluorescent amorphous organic matter and proximate dinocysts deposited in the open marine lagoon (the anoxicsuboxic environment) in agreement with general sedimentological observations. PF3 has a high diversity of dinocysts, combined with the terrestrial material. A diverse dinocyst assemblage is common in shelf environments, leading us to interpret a possible inner to middle shelf close enough to land to allow accumulation of terrestrially derived organic material.