Naturally fragile drylands are between the most sensitive regions with respect to climate change and human activities. More than 80% of Iran are drylands today, and the country formed a natural bridge from southwestern to southern and central Asia for human migrations. However, geomorphic and paleoenvironmental changes in the drylands of eastern and northeastern Iran were hardly studied so far, what holds especially true for fluvial archives in river basins with catchments of several hundreds to thousands of square kilometres. To fill this gap, during a field expedition in march 2019 we investigated a part of the Kashaf Rud river valley in northeastern Iran to build up a first field-based outline of the Quaternary geomorphic landscape evolution, and thereby to offer a first geomorphic frame for human migrations in this part of a main human migration corridor. In agreement with former results that were obtained during archaeological excavations, our preliminary field findings demonstrate three main morphological terrace levels with well-outcropped sediments. According to Lower Paleolithic archaeological findings from the upper part of uppermost terrace level T3, the gravelly to silty material of this level must have been aggraded during the Early Quaternary. Given the overwhelming dominance of yellowish to ocherous loamy to silty material in the sediments of terrace level T2, this suggests that they mainly originate from reworked aeolian loess that is known since the Middle Pleistocene in northern Iran. A paleosol developed in its sediments indicates a multi-phased aggradation that was interrupted by at least one period of floodplain stability with soil formation. Furthermore, the intensive paleosol that overprinted the sediments of level T-2 was covered by thick slope sediments, indicating an intensive geomorphic dynamics after terrace formation. Whether this phase was concomitant with the formation of the lowest silty-loamy terrace level T-1 is not clear yet. Here we just present a basic framework for the Quaternary geomorphic landscape evolution of the Kashaf Rud river valley, whereas its evolution must have been much more complex. Our study demonstrates the high value of the Kashaf Rud valley for investigations of Late Quaternary geomorphic and paleoenvironmental changes in the drylands of eastern and northeastern Iran. However, the question remains whether so-far largely missing post-Lower Paleolithic findings in this part of the human migration corridor are linked with those geomorphic landscape changes.

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