Facies architecture and origin of the Quaternary sand dunes of the Qazvin Plain, Iran

Sand dunes of the Quaternary age occupy large areas of Iran’s semiarid and arid regions. In this study, some 33 sediment samples were collected from the crest, the lee and stoss sides of the linear dunes of the southern part of Qazvin plain. Sedimentological, geochemical, and mineralogical investigations were carried out in order to identify the origin and probable source of the aeolian dune sands. Grain size analysis of the sediments shows that most of the aeolian sands are generally fine-grained, moderately well-sorted, fine skewed and leptokurtic. The textural, mineralogical and the geochemical results supported by the statistical approach indicate that the dune sands were mainly derived from the Quaternary flood plain with a minor contribution from alluvial and fluvial sands. Facies study leads to the determination of 4 facies in 2 facies associations, including: 1) medium-grained lithofacies (Sdpc, Sdl, and Sdm), and 2) gypcrete facies (G). The studied aeolian sands are characterized by the predominance of gypsum and quartz, and stable minerals together with sedimentary, metamorphic, and volcanic fragments, and a few unstable pyroxene and amphibole minerals. The sand dunes of the Qazvin Plain record a semi-arid to arid paleoclimate and the relatively stable tectonic background characterized by the mineralogical and geochemical composition and gypcrete facies in the dunes.