Biostratigraphy and study of paleodepth changes of the Gurpi Formation deposits based on planktonic foraminifera in the Bagh-gol section, Lurestan area, Zagros Basin
Subject Areas :Ayoub Bazvand 1 , A. Sadeghi 2 , M.H. Adabi 3 , A.M. Jamali 4 , N. Hadavandkhani 5
1 - Ph.D student of Shahid Beheshti University
2 -
3 -
4 -
5 -
Keywords: Biostratigraphy, Gurpi Formation, Paleodepth, Planktonic foraminifera, Sultan Anticline,
Abstract :
In order to study the biostratigraphy of the Gurpi Formation deposits in the northeast of the Lurestan region, a stratigraphic section (Bagh-gol section) from the Gurpi Formation in the Sultan anticline was selected and sampled. The Gurpi Formation in this section is 310 meters thick and is lithologically composed of argillaceous and marly limestones, marl, and shale. Two formal members of the Seymareh and Imam-Hassan limestones are present in this section. The lower boundary of the Gurpi Formation with the Ilam Formation is conformable, and there are iron oxide compounds at boundary. Its upper boundary with the Pabdeh Formation is discontinuous and conformable. In the biostratigraphic study, 74 species belonging to 30 genera of planktonic foraminifera were identified. 7 biozones in the Gurpi Formation and 1 biozone at the base of the Pabdeh Formation were identified and introduced. Based on the identified biozones, the age of the Gurpi Formation was determined to be mid to late Early Campanian-Late Maastrichtian. The statistical study of the ratio of planktonic to benthic foraminifera and also their placement in the morphotypes of planktonic foraminifera during the sedimentary sequence of the Gurpi Formation showed changes in the paleodepth of the sedimentary basin. Based on this, it was determined that the depth of the sedimentary basin decreased in the middle Campanian and increased in the upper part of the Campanian and the beginning of the Maastrichtian, and then gradually decreased until the end of the Maastrichtian.