Investigating microfacies and sedimentary environment of the Shahbazan Formation in the Lorestan Basin

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.