Abstract The Shahbazan Formation is dated to the middle to late Eocene age, after the Pyrenean orogenic phase. Following the progression of seawater, it was deposited in the Lorestan subzone and the folded Zagros basin. The lithology of this formation is composed of weathered white to thick-bedded, porous, and sugar textured, brown dolostones and dolomitic limestones. The thickness of this formation at the Darabi, Maleh Kuh, Langar, and Chenareh sections is 289, 269, 309.7, and 294 meters, respectively. In the Darabi, Maleh Kuh, and Langar sections, the lower boundary of the Shahbazan Formation is disconformity with the Kashkan Formation and overlain by the Asmari Formation with discontinuity. Furthermore, only in the Chenareh section does the Shahbazan Formation overlies conformably on the Pabdeh Formation and is overlined with a disconformity surface by the Asmari Formation. Microfacies studies revealed 12 microfacies within the Chenareh, Langar, Poshtejangal (Darabi section), and Maleh Kuh anticlines, deposited in five sedimentary environments (facies belts), including open marine A, bioclastic shoal B, lagoon C, tidal zone D, and supratidal F. These environments are part of a ramp-type carbonate platform with a uniform slope in the inner and middle ramp. Keywords: Sedimentary Environment, Shahbazan Formation, Lorestan Zone, Folded Zagros Introduction During the early Tertiary, the Zagros basin was covered by marine transgression, and the Pabdeh Formation, which consists of shale and marl, was deposited in the deep parts of this basin. Afterward, it was eventually covered with shallow carbonate deposits of the Asmari and Jahrum formations in various areas. The deposits mentioned earlier were covered with evaporites of the Gachsaran and coarse-grained clastic deposits of the Aghajari and Bakhtiari formations. Finally, the existing sediments were folded due to the collision of the Arabian and Eurasian plates during the Cenozoic. In addition, the closure of the mentioned basin led to the formation of the Zagros collision mountain range, which forms part of the Alpine-Himalayan collision zone (Alavi 2004; Navabpour et al. 2012). The Shahbazan Formation is a carbonate unit that extends only in the Lorestan subzone and the northeastern part of the Dezful depression. The studied outcrop of this formation is located in Shahbazan village, southeast of the Lorestan subzone, (next to the Andimeshk–Dorud railway). The type section is also situated in continuation of the Tele-Zang Formation in Tang 2, 4.5 kilometers southwest of the Tele-Zang rail station (Aghanabati 2011). The Shahbazan Formation is stratigraphically situated in the central and northern regions of the Lorestan structural subzone. This formation is wrapped between the red conglomerates and siltstones of the Kashkan Formation and the limestones of the Asmari Formation, which makes it possible to easily access the succession of the Shahbazan Formation. Since it is challenging to separate the Shahbazan and Asmari formations, they are referred to as Shahbazan-Asmari, and their boundaries can only be determined by paleontological studies. Moreover, one of the primary objectives of this study is to investigate the changes in the sedimentary environment of this formation along the northwest-southeast trend in the Lorestan subzone. Parts of the Lorestan subzone contain sediments related to both the shallower part of the anticline basin (Maleh Kuh anticline) and the deeper part of the anticline basin (Chenareh anticline). Moreover, the lower side of the fault that enters the Dezful Depression subzone contains sediments from deeper parts of the basin (Zabihi Zoarem et al. 2016). Therefore, this region is an appropriate location for studying the evolution of the Shahbazan basin. In Maleh Kuh and Darabi anticlines, the Shahbazan Formation is situated on the Kashkan Formation. As the basin deepens to the southeast, it changes to the Pabdeh Formation. Accordingly, this research examines the stratigraphy, microfacies, and sedimentary environment of the Shahbazan Formation in four outcrop sections of Darabi, Maleh Kuh, Langar, and Chenareh in order to achieve the above goals. Material & Methods From four surface sections of the Shahbazan Formation within the Lorestan subzone, 480 thin sections were prepared. Samples of four sections were collected at intervals of one to two meters, taking into account each section's lithological conditions and stratigraphic properties individually. After preparation, the thin microscopic sections were examined using a polarized microscope in the laboratory. This study used Dunham's classification method to nomenclature carbonate rocks (Dunham 1962). In addition, the sedimentary environment was identified by analyzing foraminifera and their abundance. Facies belts were classified in terms of the facies types using Wilson's (1975) and Flugel's (2010) classifications. The sedimentology and paleontology characteristics of four surface sections were used to identify the facies and sedimentary environments. Discussions of Results & Conclusions The following conclusions were drawn based on studies conducted on the studied outcrop sections of the Shahbazan Formation, analyzing the information obtained in terms of lithostratigraphy and biostratigraphy, as well as assessing and investigating microfacies. Biostratigraphic evidence shows that based on biostratigraphy studies and adaptation of studied biozones and identification of two biozones of Somalina sp zone and Nummulites-Alveolina Assemblage zone (Wynd 1965), which are equivalent to the biozones SBZ19 and SBZ18 (Serra Kiel et al. 1998), the age of Shahbazan Formation in Langar anticline and Chenareh anticlines located in the southeast of Lorestan and other areas close to them is middle to late Eocene. The Shahbazan and Asmari formations in the Maleh Kuh and Pusht-Jangal anticlines have been mapped under the title Shahbazan-Asmari due to their striking resemblance in appearance and, of course, crystallization in many parts. Nevertheless, it is suggested that the Shahbazan Formation dates from the mid-to-late Eocene based on the stratigraphic position. The present study has shown that the Shahbazan Formation can be divided into three units in the Maleh-Kuh anticline. Unit 1 is composed of dolostones with interlayers of limestones and marls. Units 2 and 3 are made up of thin and medium-bedded limestones, respectively. The age of the third unit was determined based on the Borelis melo melo species (Burdigalian). It should be noted that units 1 and 2 do not contain fossils, but the stratigraphic position suggests that unit 1 was formed in the middle to late Eocene, while unit 2 dates from the Aquitanian. The dolomitization of the Shahbazan Formation accelerates from the southeast to the north of the Lorestan Basin, with its maximum thickness which is visible in the Pashtu-Jangal anticline. Facies analysis of samples of the Shahbazan Formation in the Chenareh, Langar, Pusht-Jangal (Darabi section), and Maleh Kuh anticlines led to the identification of 12 microfacies, which were deposited in five sedimentary environments (facies belts) including open marine A, bioclastic shoal B, lagoon C, subtidal D and supratidal F (Flugel 2010). These environments are part of a ramp-type carbonate platform with a uniform slope in the inner and middle parts of the ramp.