Sequence stratigraphy of Albian–Campanian carbonate deposits (Sarvak and Ilam formations) in Shiraz area, Fars, SW Iran

Abstract

Bangestan group in SW Iran consists of Sarvak and Ilam formations. The Sarvak and Ilam formations comprise a thick succession of carbonate rocks in Zagros basin of Southern Iran. These formations form one of the main hydrocarbon reservoirs in central Fars, Shiraz area. This study presents a facies analysis, sedimentary environments and sequence stratigraphy. To study petrography, microfacies, sedimentary environments and sequence stratigraphy of Sarvak and Ilam formations one stratigraphic section has been chosen and studied (MajAbad section). Facies analysis led to recognition of 13 microfacies and 2 lithofacies. Study of microfacies components such as allochems and ortochems, relative sea level change and sequence stratigraphy evidences show these facies were deposited in carbonate ramp sedimentary environment in 4 facies belt zones: open marine (A), Shoal (B), Lagoon (C) and Tidal flat (D) during Middle Creataceous. Petrography, microfacies analysis and sedimentary environment of Sarvak and Ilam formations show these formations in study area consist of 5 3 order depositional sequences. Sequence 1 to sequence 4 related to Sarvak Formation and sequence 5 covered of Ilam formation. These depositional sequences have been seperated by both type-1 and type-2 sequence boundaries. Sequence stratigraphy evidences show that the Sarvak and Ilam Formations constitute five separate depositional sequences which are separated by a thin palaeosol, representing a type-one and type -two sequence boundary which can be correlated with global curves of relative sea-level.