Sequence stratigraphy and platform to basin margin facies transition of the Lower Cretaceous Dariyan Formation (northeastern Arabian Plate, Zagros fold-thrust belt, Iran)

Abstract

The Lower Cretaceous (Aptian-Albian) Dariyan Formation (northeastern Arabian Plate, Iran) represents the youngest sediments of the Khami group in the Zagros fold belt. This study is based on six sections located in the Izeh Zone and Interior Fars Province documenting transition from platform to a basin margin facies. Three assemblage zones based on benthic foraminifers have been identified and provide an early Aptian-early Albian age. Petrographic and microfacies analyses characterize thirteen carbonate microfacies and two mud rock lithofacies-types. The vertical and lateral facies variations observed in this study for the Dariyan Formation are in agreement with a depositional environment going from a homoclinal carbonate ramp to margin of intra-shelf basin type. Based on the identification of three sequence boundaries (SB), the Dariyan Formation sediments has been divided into three 2 nd -order depositional sequences which encompasses six and five 3 rd -order sequences in the margin of intra-shelf basin and the shallow platform settings, respectively. The early Aptian sea-level rise led to the extension of the carbonate platform and deposition of pelagic facies as a maximum flooding surface on margin of intra-shelf basin. In the late Aptian highstand phase, the platform was exposed as a result of glacio-eustatic mechanisms, whereas sediments continued to accumulate in the margin of intra-shelf basin. This study supports the general paleogeography of the studied area documented by previous studies and provides better insight to the interpretation of the evolution in this area and other similar basins.