Depositional history of the uppermost Albian–Turonian Sarvak Formation in the Izeh Zone (SW Iran)

Abstract

The uppermost Albian–Turonian interval has been studied in the south of the Izeh Zone (SW Iran) to investigate the depositional history of the Sarvak Formation in this area. This interval in the Middle East is characterized by the presence of very large shallow water carbonate platforms, surrounding the intra-shelf basins. The expansion of up to 90% hemipelagic strata throughout the studied outcrop proposes that it has been deposited in an intra-shelf basin. Three Cenomanian and one Turonian depositional sequences were distinguished in the studied interval based on the alternation of three microfacies associations including oligosteginid-dominated, oligosteginid-free, and platform-top microfacies. The biostratigraphical calibration by means of the planktic foraminifera indicates that these sequences can be well correlated on a global scale. The simultaneous influence of eustatic, tectonic, and environmental factors on the depositional sequences in the Lar Anticline section makes it difficult to identify the dominance of one over the others. The ability to correlate the sequence boundaries in the studied section with the global events suggests the effect of eustasy on the deposition of this interval. However, the tectonic control by the creation of a paleo-depression, subsidence (during the TST of Sequence 3), and uplift (at the Cenomanian/Turonian boundary (SB4) and mid-Turonian (SB5)) overprinted the eustatic factor. The influx of clay and the black shale formation during OAE2 conditions are the environmental factors that cannot be ignored in the deposition of sequence 1 and sequence 3, respectively.