Size does not matter: Glacial record on quartz grains from Pleistocene glacial deposits in Tatra Mts. (Western Carpathians) revealed by scanning electron microscopy

Abstract

Microtextures on sand-sized quartz grains can indicate their depositional environments. Glacial tills typically contain grains with abrasion and crushing microtextures, which are considered most intense in subglacial settings. These microtextures were previously thought to vary with ice thickness, transport distance, and basal shear stress. However, the conditions necessary to modify quartz grain morphology in glacial environments remain unclear. In this study, we show that glacier parameters do not directly control quartz grain comminution. We analyzed tills deposited before, during, and after the Last Glacial Maximum (LGM) from five Pleistocene glacial systems in the Tatra Mts. (Western Carpathians), identifying glacially-induced microtextures. The frequency of grains with abrasion and crushing microtextures does not correlate with glacier length (2.3–13.4 km), maximum ice thickness (100–420 m), or basal shear stress (73–151 kPa). We further demonstrate that at least two glacial stages (pre-LGM and LGM) can be distinguished within a single sample based on microtextures preservation (freshness). Additionally, we describe a newly recognized microtexture type: the rosette fracture. Our findings suggest that abrasion and crushing microtextures in warm-based glaciers are primarily influenced by substratum lithology, sediment texture, and till origin, rather than glacier size or dynamics. Even small glaciers (1–2 km²) with short transport paths (2–3 km) are capable of effectively abrading and fracturing quartz grains. Under favorable conditions, well-preserved glacial microtextures from Middle Pleistocene mountain glaciers can still be detected. Detailed SEM analysis thus provides valuable insights into past glaciations and the minimum number of glacial cycles, even in moderately glaciated mountain regions.