Biostratigraphy and depositional environment of the Asmari Formation in Gachsaran Well No. 25

Document Type : Original Research


1 Department of Geology, Faculty of Science, Lorestan University, Lorestan, Iran

2 Geology Section of Iranian National Oil Company of Southern Oilfield District


The Asmari Formation has been studied from biostratigraphic and depositional environment point of view in well No. 25, Gachsaran oil field. The thickness of the Asmari Formation in well No. 25 is 632 meters. The study of 220 thin sections taken from the studied well led to the identification of 47 genera and 48 species of benthonic foraminifera. According to the index foraminifera such as Eulipidina sp., Nepherolepidina sp., Borelis melo curdica., Miogipsinoides complanatus, the age of the Asmari Formation, studied in the subsurface, ranges from Oligocene (Rupelian-Chattian) to Early Miocene (Aquitania- Burdigalian). 10 carbonate microfacies were also identified within the Asmari Formation, well No. 25. The microfacies belong to the shallow open marine, barrier, restricted lagoon and lagoon environment.