First record of Reticulinella? kaeveri in the Laffan and Ilam formations (Zagros fold and thrust belt, SW Iran): new constraints on the chronostratigraphic calibration of the Arabian Plate sequence stratigraphy

Abstract

Over the past two decades, sequence stratigraphy has proven to be a valuable tool in addressing challenges arising from the inconsistent application of lithostratigraphic nomenclature across diverse geological provinces. It has been particularly successful in achieving regional correlations within the Cretaceous deposits of the Arabian Plate. The key sequence stratigraphic surface in the currently adopted standard sequence stratigraphic scheme is the K150 SB, marking the transition from a passive to an active margin along the eastern edge of the Arabian plate. Despite its importance, the chronostratigraphic age of this surface is poorly constrained. In the Zagros FTB, the uppermost part of the Sarvak Formation, just below the K150 SB, was recently assigned to the upper part of middle Turonian to upper Turonian, based on the presence of Reticulinella? kaeveri. Our research reveals that the range of R.? kaeveri extends above the K150 SB as this species is also present in the Laffan and base of Ilam formations. The Last Occurrence of this taxon provides a new chronostratigraphic marker of the upper Turonian within the Ilam Formation. This finding proves that more Turonian deposit are present in the study area than was previously recognized. We have studied the deposits enclosing the K150 SB in outcrop sections and wells along a transect from basin to platform margin to inner platform setting. Based on planktonic foraminifera and calcareous nannofossils biostratigraphy of basinal sections and sequence stratigraphic correlation to carbonate platform sections, the age of the uppermost part of the Sarvak Formation, immediately below the K150 SB, is firmly constrained within the interval lower Turonian–lower part of middle Turonian. Sequence stratigraphic correlation from basin to platform interior reveals also that the oldest deposits above the K150 SB are not younger than late Turonian. Our new data represents a significant improvement in the chronostratigraphic calibration of sequence stratigraphy in the Cretaceous of the Zagros fold-and-thrust belt.