Palaeoenvironment and geological evolution of a late Quaternary lacustrine-palustrine carbonate complex: Zaranda Basin, Saveh, Central Iran

The continental carbonate deposits of the Zarand Basin were deposited within an intra-continental strike-slip basin situated in the northwestern corner of central Iran. They consist of distal alluvial mudstones to marlstones, carbonate pond deposits, carbonate and siliciclastic-infilled channels, and lacustrine carbonates deposited within a distal alluvial–lacustrine–palustrine complex. Both sedimentological and palaeontological evidence suggest that these sediments mostly formed within an open hydrological system. The common presence of root traces, greyish green mudstones, calcareous nodulisation, mottling, and desiccation breccias indicate a palustrine setting. The carbonate deposits of the Zarand Basin were formed under an overall semi-arid climate but periods of more aridity characterised by extensive calcretization can be distinguished in the stratigraphical sections. Both tectonics and climate have contributed in controlling the sedimentation of the Zarand Basin. Archaeological and geomorphological evidence provides a unique sub-recent analogue for ancient palustrine limestones developed within an intra-continental basin under a semi-arid climatic regime. The combination of geological and archaeological data and their comparison with historical documents show that the socalled historical lake of Saveh was the remnant of the more ancient wetland system which dominated the Zarand region during the late Quaternary.