The Asmari Formation is a geological formation in western Iran. Located in the western Zagros Mountains, it is a carbonate formation that largely consists of limestone, dolomitic limestone, dolomite, and marly limestone. [1] There are also smaller amounts of anhydrite, lithic sandstone, and limey sandstone. [1] The formation dates to the Oligocene and Miocene periods and is a major hydrocarbon reserve. [2] [3] It has been producing oil since the 1930s. [4] It also forms a major aquifer, which discharges at various springs in the Zagros region. [5]
The Asmari Formation's basic biostratigraphy was established in the 1950s and it was formally described in 1965. [4] It consists of carbonate platforms that were formed in 6 distinct stages. [3] The formation is named after the Asmari Mountains southeast of Masjed Soleyman, and its type sample was taken from the Tang-e Gel Torsh in these mountains. [6]
The Asmari Formation was deposited at a time when the Tethys Ocean was finally closing and the Zagros Mountains were first rising. [6] During this period, the region was a shallow ocean gradually getting less deep. [6] By the time of the succeeding Gachsaran Formation, this process had culminated in the sea shrinking to lagoons. [6]
In the southwestern Zagros, the Asmari Formation sits on top of the Pabdeh Formation. [1] In the Fars and Luristan regions, the Asmari Formation sits on top of the Jahrum and Shahbazan Formations. [1] The Asmari Formation is thickest in the northeastern part of the Dezful Embayment. [1]
The formation has various microfossils including planktonic foraminifera, echinoids, red algae, ostracoda, and oncoids. [3] Individual species include Globigerina , Turborotalia cerroazulensis, Hantkenina , Nummulites , Lepidocyclina , Miogypsina , Elphidium , Peneroplis farsenensis, and Borelis melo curdica and Borelis melo melo. [4]
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