The Mehriz Sand Ramps: A Late Quaternary Palaeoenvironmental Archive of Extreme Aridity and Glacial Legacy in Central Iran.

This study examines the influence of late Quaternary climate changes, local topographical features, and wind dynamics on the formation, development, and activity of sand ramps situated south of Yazd, Central Iran. Research methods included extensive fieldwork, geomorphological and geological mapping, thin-section analysis, XRD studies, and evaluation of regional wind and precipitation data. The ramps formed under rapidly changing arid conditions during the late Quaternary, as indicated by the poorly weathered and unconsolidated aeolian sands and the absence of alluvial or colluvial layers within the deposits. Their formation and evolution were strongly controlled by topography, lithology, wind patterns, and episodes of extreme cold and aridity. Mineralogical analyses show dominant quartz, feldspar, mica, and biotite in the lower sand sheet layers, pointing to a source from mafic rocks outcropped in glacial cirques and valleys above 2,200 m a.s.l. These rocks weathered during glacial periods, and the resulting sediments were transported downslope by ice tongues and runoff. During subsequent arid periods, winds redistributed the finer sediments over short distances, depositing some as sand sheets at the base of slopes, while others were carried up mountain slopes or across ridges to accumulate on the leeward sides. A shift from mafic minerals in the lower layers to calcite-rich surface layers reflects a change in environmental conditions over time. The current limited activity of the ramps suggests they are relict features, formed during past periods of intense drought, when extreme aridity provided the necessary conditions for their accumulation.