A Stratigraphic Development of the Upper Oligocene - Middle Miocene succession in Wadi Heglan, Western Iraq

Abstract

The Upper Oligocene -Middle Miocene succession in Wadi Heglan, western Iraq was carried out to study microfacies and paleoenvironment. The Anah and Euphrates formations are exposed in this section. Anah Formation consists of massive, coralline, and dolomitic limestone, while the Euphrates Formation consists of massive and become well bedded upwards, obvious porous, marly, and dolomitic limestone. The abundance of benthic foraminifera and other fossils within these facies, the appropriate paleoenvironment for the Anah and Euphrates formations were determined. The reef and back-reef environments are recognized Anah Formation and the restricted to open marine environments are recognized Euphrates Formation. The Anah Formation exposed in this section by long episode of high stand trace (HST) which represent fall sea level of back-reef facies, while Euphrates Formation was deposited during three fourth-order cycles (A, B, and C), these cycles represent a succession episode of sea level rises (TST) and stillstands (HST). These sequences are bounded by two type-1 sequence boundary SB1. The area of study show very low rate of subsidence according to sequence development and the main factors that affect the study area is the fluctuation of eustatic sea level..