ON THE MECHANISMS OF MINOR MORAINE FORMATION IN HIGH-MOUNTAIN ENVIRONMENTS OF THE EUROPEAN ALPS

Abstract

Groups of closely spaced minor moraines allow for observations of moraine formation and ice-marginal fluctuations on short timescales, helping to better understand glacier retreat and predict its geomorphological effects. Some minor moraines can be classified as annual moraines given sufficient chronological control, which implies a seasonal climatic driver of ice-marginal fluctuations. This leads to moraines being utilised as very specific, short-term records of glacier fluctuations and climate change. This research is common in lowland, maritime settings, but remains sparse in high-mountain settings. This study presents the detailed geomorphological and sedimentological results of minor moraines at two high-mountain settings in the European Alps. Geomorphological investigations included mapping and measurements through field observations and remotely-sensed imagery. Detailed sedimentological investigations followed excavation of moraines and include multiple scales of observation and measurements to support interpretations of sediment transport and deposition. Additionally, ground-penetrating radar data were collected in one foreland. Minor moraines at Schwarzensteinkees, Austria, formed as push or combined push and freeze-on moraines in two groups between approximately 1850 and 1930. The existence of a former proglacial lake appears to have exerted a strong control on moraine formation. Modern minor moraines at Silvrettagletscher, Switzerland, exist primarily on reverse bedrock slopes and have formed since approximately 1850 through push, freeze-on, and controlled moraine mechanisms. The presence of these bedrock slopes, and in some areas englacial debris septa, appear to exert the primary controls on moraine formation. The foreland of Gornergletscher, Switzerland, has been revisited using aerial imagery to assess if moraines are still forming annually, and this has been confirmed. These findings show a range of mechanisms responsible for moraine formation, which are then compared to previously published research on minor moraines to elucidate any common drivers of minor and annual moraine formation globally. This includes a global database of forelands where minor moraines have been studied, created as part of this research and presented as a table and Google Earth file, both easily accessible and freely available online, for use by other researchers when exploring similar topics.