ISSN 0869-5938, Stratigraphy and Geological Correlation, 2016, Vol. 24, No. 3, pp. 267–275. © Pleiades Publishing, Ltd., 2016. 267 1 INTRODUCTION The Zagros Basin is one of the most important oil and gas reservoirs in the world. This basin has long been studied by many researchers. Many formations in the southeast of Zagros zone are the hydrocarbon reservoirs. The Guri Member of the Mishan Forma- tion contains a significant amount of gas in some areas (Alsharhan and Nairn, 1997). The Bandar Abbas hin- terland is one of significant areas that are located in the southeast Zagros. The eastern boundary of this hinter- land is Minab fault, and its southern border crosses through the Persian Gulf region. The most important geological features of the Bandar Abbas hinterland are the anticlines with different orientation and structural changes which can be attributed to the basement faults. The anticlines consist mostly of Fars Group with a remarkable thickness (Aghanabati, 2006). The Mishan Formation as one of the formations of the Fars Group was introduced by James and Wynd (1965). Previously, the Guri Member of this formation has been called by different names, for instance, Guri Formation and Operculina Limestone. Its type sec- tion, 111-m thick, is located in Tang-e-Guri, 28 km 1 The article is published in the original. southeast of the Lar and is composed of rough, mas- sive, and hard creamy limestone. This part of the Mis- han Formation contains numerous fossils including micro- and macrofossils (foraminifers, ostracods, red algae, and mollusks) with some interbedded gray to green marl. This member overlies siliciclastic rock of the Razak Formation or the Evaporate Formation of Gachsaran. The lower boundary with the Gachsaran Formation is disconformable and sharp and its upper boundary with green and gray marls of the Mishan Formation is conformable and gradual. Thickness of the Guri Limestone is variable, for example, in the Bandar Abbas hinterland it increases to 1200 m but decreases from Fars toward Khuzestan, and it is invis- ible in the northwest of the Kazerun fault (Aghanabati, 2006) (Fig. 1). Daneshian et al. (2008) studied litho- logical features of the Guri Member in 15 subsurface and outcrop sections at the Dezful Embayment located in the Khuzestan Province. They reported that the thickness reduces in the studied areas from south- east to northwest. They stated the maximum thickness of this rock unit at approximately 192 m. Wynd (1965) introduced biofacies no. 64 for the Guri Limestone and the overlying no. 65 for marl sedi- ments of the Mishan Formation. The biofacies no. 64 Refinement of Stratigraphy According to the First Finds of Planktonic Species of Orbulina and Praeorbulina from the Guri Limestone of the Mishan Formation in Northwest of Bandar Abbas, South Iran 1 J. Daneshian a , S. A. Moallemi b , and M. Derakhshani a a Department of Geology, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran b Reservoir Geology Division, Exploration and Production Department, Research Institute of Petroleum Industry, Tehran, Iran e-mail: daneshian@khu.ac.ir Received February 16, 2015; in final form, March 29, 2015 Abstract—The Zagros Basin is one of the most universal oil and gas basins that is located in the west to south of Iran and in north of the Arabian Plate. The Guri Member at the bottom of the Mishan Formation, in some areas such as Bandar Abbas hinterland, contains a significant amount of gas. The Bandar Abbas hinterland is located in the southeast of Zagros. The Guri Limestone is the youngest hydrocarbon reservoirs of the Zagros Sedimentary Basin. In this study, a total of 178 samples from the Guri Limestone in the Handun section are investigated for foraminiferal biostratigraphy. The study of foraminifers led to a recognition of 43 genera and 57 species of benthic and planktonic foraminifera. For the first time, planktonic foraminiferal species includ- ing Praeorbulina glomerosa, Praeorbulina transitoria, Orbulina suturalis, and Orbulina universa are reported, and based on the identified benthic and planktonic foraminifera taxa, the age of the Guri Member at Handun section is estimated as late Burdigalian to Langhian. Keywords: Planktonic foraminifers, biostratigraphy, Early and Middle Miocene, Mishan Formation, Zagros Basin, Iran DOI: 10.1134/S0869593816030023