Lithostratigraphy and biostratigraphy of the Upper Dalan and Lower Kangan 52 units in Persian Gulf with special emphasis on the Permo/ Triassic boundary

The Upper Dalan and Lower Kangan stratigraphic units with 225m thickness were studied in one of the subsurface section in Persian Gulf area. According to the biostrarigraphic investigation on the dolomitic and limestone successions of the Upper Dalan unit, there are more than 30 index foraminifera and non-foraminifera species. One Paradagmarita/ Paraglobivalvulina/ Baisalina Assemblage Zone that divided to three distinct sub- assemblage zones1. Rectostipulina quadrata/ Globivalvulina vonderschimitti Assemblage subzone2. Dagmarita chanackchiensis/ Ichtyolaria latilimbata Assemblage subzone3. Hemigordiopsis renzi/ Paradagmarita flabeliformis Assemblage subzonehave been distinguished in the stratigraphic section representing the Julfian to Earleast Dorashamian stage. The identified microfauna' assemblages can be corresponded to the Late Permian regional biozonation in the Tethys realm. The latest microfauna assemblages in the latest part of Dalan Formation exhibits a significant chronostratigraphic hiatus, just was cited in the Dalan/ Kangan (Permo/Triassic) boundary. There is no any evidence about Latest Dorashamian sediments in the study area. The Permo/Triassic boundary is a paraconformity type in the latest Permian biozones, which can be corresponded to other areas of the world. The Lower Kangan stratigraphic unit can be attributed to the Schytian age (Early Triassic age) on basis of presence of some index fossils such as Bivalves (Claraia sp.) and Serpulids (Spirorbis sp.). It should be stressed that the similar microfauna associations can be seen in other Iranian places such as Central Iran and Alborz areas, which is documented a distinct palaeobiogeographical relationship between the above-mentioned areas and Zagros realm on Permian and Triassic ages.