Micro‐Scale Frost Weathering of Sand‐Sized Quartz Grains

The surface textures of almost 1300 quartz grains in the 0.8–1.0 mm and 0.5–0.8 mm size fractions were studied in order to analyse the effects of frost weathering. Some grains had undergone periglacial processes in present‐day active layers in Canada, Spitsbergen and Mongolia, whereas other grains were sampled from a former active layer in Poland. Microstructures were studied under a scanning electron microscope and the results statistically analysed in order to distinguish characteristic microstructures resulting from frost weathering. The quartz grains with these microstructures had been deposited by fluvial, aeolian and glacial processes and their characteristic microstructures are classified as primary microstructures. Microstructures that developed on primary ones as a result of frost weathering are called secondary microstructures. The most characteristic secondary frost weathering microstructures on the quartz grains are (1) small breakage blocks (<10 µm), (2) big breakage blocks (>10 µm) and (3) single small conchoidal fractures (<10 µm). These secondary microstructures developed commonly on the following primary microstructures: (1) sharp edges of big conchoidal fractures (>10 µm), (2) microsteps, (3) edge roundings and (4) crescentic gouges. These findings facilitate the reconstruction of cryogenic conditions, support the recognition of ancient active layers and indicate grains that are particularly susceptible to frost weathering. Copyright © 2015 John Wiley & Sons, Ltd.