Little information is available on the paleoclimate evolution of northeast Iran relating to global cold and warm stages. The loess/paleosol sequences from southern Mashhad and Kalat-e Naderi areas were studied to determine the landscape evolution and to set up the first chronological framework for the Pleistocene deposits in northeast Iran. The loess deposits in these areas are less thick (up to 12 m) and have a more patchy distribution than in the Caspian Lowland of northern Iran. Infrared stimulated luminescence (IRSL) dating of loess or loess derivatives from the Robat-e Khakestari, Tappeh Salam and Deh Gheybi sections (a) and (b) from southern Mashhad, as well as Kalat-e Naderi sections (a) and (b) in Kalat-e Naderi area provides a more reliable chronological framework for climate and environmental changes taken place over for the time period including the penultimate and last interglacial/glacial cycles. The Robat-e Khakestari section, the Kalat-e Naderi sections (a) and (b), and to some extent the Tappeh Salam section include loess/paleosol sequences, which are chronologically in excellent agreement with the loess record of the Caspian Lowland in northern Iran. The Deh Gheybi sections (a) and (b) include loess-like sediments and fluvial deposits that make their interpretation difficult. Loess accumulated during MIS 2 at the Robat-e Khakestari section and at the Kalat-e Naderi sections (a) and (b) suggesting a more windy and arid Last Glacial Maximum (LGM) in northeast Iran. Paleosols, correlating most likely with MIS 5, were covered by fluvial sediments at the Kalat-e Naderi section (a). The absence of loess deposits correlating to MIS 3 and MIS 4 at the Robat-e Khakestari section is very likely to have been caused by fluvial processes and water erosion.

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