Loess origin and late Pleistocene environmental reconstruction for northeastern Iran: Multiproxy evidences from the Chenarli loess-paleosol sequence.

Little information is available about the origin of loess on the Iranian Loess Plateau and along the northern foothills of the Alborz mountain range. Our well-dated multiproxy record from the Chenarli loess-paleosol sequence (LPS) fills this gap and provides a valuable paleoclimate record. Eight loess units are identified , covering the late penultimate glacial period (Marine Isotope Stage (MIS) 6: 135.6 ± 9.5 ka) until the Early Holocene (9.8 ± 0.7 ka). Geochemical results propose a constant local primary loess source with a longer transport distance only for MIS 5b and MIS 5d loess. However, low Si/Ti but high Zr/Ti ratios and increased sand contents of MIS 6 loess are implying stronger winds and derivation of this loess from a different source containing coarser particles. We interpret our data in a regional context and compare periods of loess deposition and pedogenesis in northern Iran with other loess records from Southern Eurasia. This indicates that late Pleistocene pedogenesis recorded at Chenarli agrees with periods of paleosol formation at LPS from northern Iran and Southern Eurasia. A ∼9-m thick loess deposition between ∼62 and 16 ka in unit 2 at Chenarli is consistent with other loess records indicating significant loess accumulation during MIS 3 with a peak during the Last Glacial Maximum in Southern Eurasia. One of the paleosols at Chenarli correlates with the late MIS 4 interstadial, which is well-recorded in southern Eurasian loess deposits. The geochemistry of loess and paleosols at Chenarli provides new information about the origin of loess in north and northeastern Iran where the sources of eolian deposition are still not well understood. • Eight loess units are identified spanning the past 135 ka, separated with paleosols. • Geochemical results indicate a constant local primary loess source for all loess units in the section. • Results indicate a longer transport distance from sources for MIS 5b and MIS 5d loess. • Particle size and geochemical data suggest that nearby sources with local sand contributions for MIS 6 loess. [ABSTRACT FROM AUTHOR]