Late Pleistocene–Holocene pedogenesis and palaeoclimate in western Asia from palaeosols of the Central Iranian Plateau

Abstract

The Late Pleistocene and Holocene in western Asia is characterized by frequent, millennial‐scale, high‐amplitude environmental climatic changes. However, little is known about palaeoclimate conditions on the arid Central Iranian Plateau and knowledge of palaeosols and past phases of pedogenesis in relation to climatic events is scarce. Nevertheless, these palaeosols contain important information on the Last Glacial–Interglacial cycle and Holocene climate and environmental changes in the region. Three representative pedons with eight argillic horizons from the interior of the Central Iranian Plateau, namely Isfahan, Jimabad and Bajestan are selected for micromorphological, mineralogical and submicroscopic analyses. The ages of these palaeosols are constrained using the optically stimulated luminescence (OSL) signal from quartz. Micromorphological observations show clay illuviation, carbonate leaching, accumulation of secondary carbonates, calcite depletion, and other characteristic pedogenic features. These characteristics, combined with the luminescence chronology, reveal the presence of well‐developed reddish‐brown palaeoargillic horizons (Btk/Btky) with intensive soil formation processes taking place during the Last Interglacial to Middle Holocene (~107–4.5 ka) in our study area. Pedogenic evidence from the palaeosols suggests steps of polygenetic formation in the argillic horizons in response to alternating wetter and drier phases during this period. Four distinct phases of pedogenesis resulting in Btk/Btky horizons are identified: (i) Marine Isotope Stage (MIS) 5, (ii) MIS 3, (iii) the Last Glacial–Interglacial Transition Holocene, and (iv) the Late Holocene.