Depositional architecture and sequence stratigraphy of the Oligo–Miocene Asmari platform; Southeastern Izeh Zone, Zagros Basin, Iran

Abstract

In the easternmost part of the main Izeh Zone<br><br>of the Zagros Mountains, Iran, the Asmari carbonate platform<br><br>system of Oligo–Miocene age is superbly exposed<br><br>in three-dimensional outcrops displaying a variety of<br><br>carbonate facies associated with well-preserved depositional<br><br>geometries. The main biogenic components of the<br><br>Asmari Formation are large benthic foraminifera, corals,<br><br>coralline algae, and planktonic foraminifera. The Asmari<br><br>carbonate platform system, based on dating by large benthic<br><br>foraminifera, biogenic components, and depositional<br><br>geometries, is divided into four distinct intervals of carbonate<br><br>platform growth. This depositional system during the<br><br>Rupelian and Rupelian/earliest Chattian was a carbonate<br><br>ramp. During the Chattian, the system was dominated by<br><br>coral buildups, and later, porcellaneous benthic foraminifera<br><br>and coralline algae were prominent during late Chattian–<br><br>early Miocene time. Six major depositional sequences<br><br>are distinguished, with an overall systematic progradation from NE to SW. These progradations are evidenced in the<br><br>Rupelian and lower Chattian by major changes in facies<br><br>and stratal architectures, whereas such complex geometries<br><br>are not observed in the upper Chattian and lower Miocene<br><br>carbonates, since only platform-top facies are exposed and<br><br>there are no outcrops of the platform margin. Comparison<br><br>of the proposed depositional sequences with those reported<br><br>in the Dezful Embayment and adjacent areas suggests a<br><br>correlation with the global sea-level curve.