Palynofacies and Palaeoenvironment of the Sanganeh Formation, East and the Center of the Kopet-Dagh Basin

Abstract In order to identify the palynofacies and to reconstruct the paleoenvironment of the Lower Cretaceous depositions in the Kopet-Dagh sedimentary basin, the Sanganeh Formation was sampled and studied. The four sections of the Sanganeh Formation were selected for correlation and comparison in the east and the center of the Kopet- Dagh Basin, respectively included Karizak, Mozduran, Sanganeh and Qarah-Su. The study of slides was done with an optical microscope. Marine palynomorphs groups, phytoclasts, amorphous organic matter, transparent to opaque amorphous organic matter ratio, brown to opaque phytoclast ratio, Peridinioid to Gonyaulacoid dinocyst ratio, abundance, and diversity of marine palynomorphs and dinoflagellates were counted and investigated. In this study, a quantitative analysis of the main palynologic elements (AOM, marine palynomorph, phytoclast) led to characterize four palynofacies types that were identified in the Karizak and Mozduran sections. Based on the palynofacies analyses and according to the plotting to Tyson diagram, we have recorded an increase in the number of phytoclasts and a decrease in the number of marine palynomorphs to the east indicating a decrease in the depth and oxygen trend in the Sanganeh Formation in these part of the Kopet-Dagh sedimentary Basin. The sedimentation rate of the Sanganeh Formation was also considered low in the studied sections. Keywords: Palynofacies, Dinoflagellate, Kopet-Dagh, Sanganeh Formation, Lower Cretaceous Introduction According to Tyson (1993, 1995) and Batten (1996b), identification of palynofacies plays an essential role in determining depositional environments as well as studying the petroleum potential in sediments. The components of palynologic slides, which are used to determine palynofacies and paleoenvironmental interpretation, can be grouped into three groups: amorphous organic matter (AOM), marine palynomorphs (MP), and phytoclasts (P). Due to the Sanganeh Formation lithology, paleontologists have been interested in working the shale samples. Several studies have been done to determine the age and identify the paleoenvironment on this formation in the Kopet-Dagh basin based on different fossil groups including foraminifera, calcareous nannofossil, ammonite, and palynomorph. Four stratigraphic sections have been selected from the Sanganeh Formation in the Kopet-Dagh Basin. The studied sections from the east to the center of the Basin are included Karizak, Mozduran, San