Depositional environment and sequence stratigraphy of the Oligo-Miocene Asmari Formation in SW Iran

Abstract

The Asmari Formation, a thick carbonate succession of the Oligo-Miocene in Zagros Mountains (southwest Iran), has been studied to determine its microfacies, paleoenvironments and sedimentary sequences. Detailed petrographic analysis of the deposits led to the recognition of 10 microfacies types. In addition, five major depositional environments were identified in the Asmari Formation. These include tidal flat, shelf lagoon, shoal, slope and basin environmental settings and are interpreted as a carbonate platform developed in an open shelf situation but without effective barriers separating the platform from the open ocean. The Asmari carbonate succession consists of four, thick shallowing-upward sequences (third-order cycles). No major hiatuses were recognized between these cycles. Therefore, the contacts are interpreted as SB2 sequence boundary types. The Pabdeh Formation, the deeper marine facies equivalent of the Asmari Limestone is interpreted to be deposited in an outer slope-basin environment. The microfacies of the Pabdeh Formation shows similarities to the Asmari Formation.

Planktonic and benthic foraminiferal biostratigraphy of the Middle Eocene–Lower Miocene successions from the Sivas Basin (Central Anatolia, Turkey)

“…shallow shelf lagoon ;Wilson 1975;Epting 1980;Flügel 1982). Almost similar foraminiferal facies were reported from the shelf lagoon or inner ramp environments in Iran (Vaziri-Moghaddam et al 2006;Amirshahkarami et al 2007;Rahmani et al 2009;Seyrafian et al 2011 andSajadi et al 2014), from NE Italy (Bassi et al 2007), from SE Turkey (Sirel 1996(Sirel , 2003 and from back reef environments in Iraq (Edgell 1997;Al-Banna 2004). In contrast to the Tuzlagözü section, the limestones enclosing the foraminiferal packstone-grainstone facies alternate with pelecypod bearing sandstone, fossiliferous (mainly ostracoda) siltstone with plant fragments, sandy conglomerate and evaporites and mudstones with planktonic foraminifera in the Egribucak section (Fig.…”

Biostratigraphy and paleoecology of the Oligo-Miocene Asmari Formation in the Izeh zone (Zagros Basin, SW Iran)

“…Our detailed analysis of the stratigraphy and paleoecology show that the Asmari Formation was deposited on a carbonate ramp in tropical to subtropical latitudes (10° to 30°) (Vaziri-Moghaddam et al, 2006;Heydari, 2008;Allahkarampour Dill et al, 2010;Vaziri-Moghaddam et al, 2010;Shabafrooz et al, 2015a, b). The differentiation between non-tropical and tropical carbonates is mainly based on analysis of skeletal components (Lees and Buller, 1972;Carannante et al, 1988;Nelson, 1988).…”

“…They did not differentiate Rupelian from Chattian. These two reports were used by many authors (e.g., Seyrafian, 2000;Vaziri-Moghaddam et al, 2006;Amirshahkarami et al, 2007a, b). Recently, Ehrenberg et al (2007), Laursen et al (2009) and Van Buchem et al (2010) conducted strontium isotope dating to improve the biostratigraphic ages for the Asmari Formation across most parts of the Zagros basin (Izeh zone and Dezful Embayment) ( Table 2).…”

Sedimentary Environment and Relative Sea Level Changes of the Asmari Formation Deposited in Lurestan Basin, Southwest of Zagros

“…Generally, these sediments are a reliable depth (i.e. relative sea level changes) index, so they can be exerted as an efficient parametere in sequence stratigraphy studies [26] and [27] in Tang-e-Gargadan, [28] in Khaviz Anticline, [29] in Dill Anticline and [30] reported similar microfacies in the Fars Platform and other parts of the Zagros.…”