Micro-scale frost-weathering simulation – Changes in grain-size composition and influencing factors

Abstract

The experimental simulation of a micro-scale frost weathering of sand-sized (0.5–1.0 mm) quartz grains has been conducted to investigate the frost-induced changes in the grain-size distributions and factors that affect the weathering process. For the first time we present the results concerning the relationship between the course of frost weathering and the characteristics of water (content and mineralization) involved in the process. The simulation involved two types of vein quartz crushed to fresh, angular grains and arranged into dry, moistened and wet samples. Grain samples were subjected to fixed temperature oscillations (from −5 °C to +10 °C) under controlled laboratory conditions. Grain-size analysis were conducted after 50, 100, and 300 freeze–thaw cycles. Differences in the distributions, resulting from the production of the frost debris, were observed at each stage of the weathering process. Statistical analyses (Kolmogorov-Smirnov test, PCA, cluster analysis) demonstrated that both types of quartz grains react differently to the ongoing weathering process regardless of the moisture conditions. The production of very coarse (1.0–2.0 mm) and coarse sand (0.5–1.0 mm) fractions, resulting from the frost-induced destruction, was observed. This issue has never been addressed or expounded before. The production of fine (0.125–0.25 mm) and very fine (0.063–0.125 mm) sands was notable while the silt-sized grains (0.002–0.063 mm) constituted only a minor product of the frost weathering. Nevertheless, the combined increase in the content of these fractions may have a significant impact on the properties of the frost-affected sediments/soils. The sample preparation (resulting in preparation defects) and the internal structure of quartz grains (resulting in primary defects) had a great influence on the initial course and manner of the frost weathering process. Other factors, such as content or mineralization of water, exerted much less influence on the frost-driven destruction during the studied weathering period.