The Reticulinella?-Mangashtia foraminiferal association: Characterisation of the (upper?) middle-?lower upper Turonian interval in the Sarvak Formation of SW Iran and its bearing upon Upper Cretaceous Arabian Plate sequence stratigraphy

During the mid-Cretaceous the Arabian Plate underwent a major tectonically-driven stratigraphic reorganization, with the development of a major regional unconformity, often ascribed to the middle Turonian. However, evidence for the age calibration of this unconformity (e.g., from biostratigraphy) is limited. A previously undescribed assemblage of larger benthic foraminifera has been discovered in a section at Khormuj in the Coastal Fars region of the Iranian Zagros. This section lies in the uppermost Sarvak Formation, directly beneath the major unconformity surface. Dominant components of the assemblage are Mangashtia viennoti Henson, and Reticulinella? kaeveri Cherchi, Radoičić and Schroeder. Their presence places the uppermost Sarvak Formation at this locality in the age range (upper?) middle – ?lower upper Turonian, and in the context of evidence from other localities in the region it is most likely upper middle Turonian. This provides new constraint on the timing of the unconformity and stratigraphic organisation, and the tectonic events leading to its creation (e.g., forebulge creation related to ophiolite obduction). The presence of R.? kaeveri is reported for the first time from outside of the Mediterranean region and indicates that this taxon is useful for biostratigraphic calibration. As a result, biozonation schemes for the upper Sarvak Formation can be updated.