Facies, depositional environments, and sequence stratigraphy analysis of the upper Barremian-lower Aptian carbonates in the northeast Kelardasht, N Iran

Abstract

The carbonates accumulated within a time interval spanning the late Barremian-early Aptian, comprise the Member 2 of the Chalous Formation. The member cropped out in the northern Central Alborz Mountains Range, northern Iran. Detailed field surveys, lithofacies and facies analyses was carried out to investigate the depositional environments and sequence stratigraphy analysis at five outcrop sections. Based on petrographic investigation and texture, sixteen facies and microfacies were defined and assigned to the back-barrier lagoon, shelf margin/shoal, and shallow open marine facies belts. Vertical and lateral facies changes, lack of several geological evidence including siliciclastics, bioherms, calciturbidites, clinoforms, together with lateral thickness changes as well as comparison to recent and ancient carbonate platforms, suggest deposition on a non-rimmed isolated carbonate platform. The upper Barremian to lower Aptian deposits of the study areas comprises three third-order depositional sequences.We infer that relative sea-level changes and climate played a deeply influential role in the platform evolution and its geometry on the base of facies analysis, vertical transition of fauna, diagenetic overprints, accompanied by stacking patterns and geometries, and correlation of the depositional sequences.