Facies Analysis and Sedimentary Model of the Upper Part of Sarmord Formation Successions Exposed in the Aqra Anticline, Northeastern Iraq

The upper unit succession of Sarmord Formation (Early Cretaceous) has been studied sedimentologically in one surface lithological section at Aqra anticline, northeastern Iraq. Based on the field data, the upper part of Sarmord Formation in the current study is composed mainly of hard limestone, dolomitic limestone, and marly limestone with thin-bedded marl. These successions are topped by Qamchouqa Formation, which is recognized by thick massive layers of limestone. Petrographically, the particle portion of the studied section is composed mainly of benthonic foraminifera, especially Miliolids, Rotaliid and others, in addition to some green algae, mollusks, bryozoans, bioclasts, lithoclasts and peliods. While the matrix is composed mainly of micrite. Generally, the studied succession is subjected slightly to some diagenetic processes like: micritization, physical compaction, cementation, dissolution, recrystallization, dolomitization and chemical compaction. Microfacies analysis has shown that the upper part of Sarmord Formation consists of three main mud-supported facies: lime mudstone microfacies, wackestone microfacies and packstone microfacies. These three main microfacies are further subdivided into eight submicrofacies. The results of the present study indicate that the succession of the upper part of Sarmord Formation was deposited in a shallow marine environment on carbonate ramp through the three zones (inner, middle and outer) ramps.