Long-term Quaternary weathering as a geomorphic agent in Alderney (Channel Islands, W Europe)

Alderney in the Channel Islands (W Europe) was never glaciated during the Quaternary but rather has been affected by long-term weathering of the underlying igneous and metamorphic rocks. This study investigates the evidence for weathering and sediment generation under mainly cold Quaternary climatic conditions, based on (1) surface geomorphology, (2) Schmidt hammer rebound values on bedrock outcrops, and (3) sediment stratigraphy along coastal sections where weathering-derived solifluction slope sediments are exposed by erosion. Results show the dominance of cold-climate features across the landscape, reflecting the role of late Quaternary periglacial weathering in producing and then mobilizing slope sediments. Both slope stratigraphy and evidence from Schmidt hammer data suggest several phases of weathering activity, but their precise timing is not yet known. Although changes in Quaternary climate (temperature, humidity) and sea level are the most likely drivers for both weathering and slope sediment supply, it is likely that this was not a simple relationship, for example, where there is progressive infilling of slope accommodation space over time. Investigating the relationships between weathering (sediment generation) and slope (sediment deposition) processes, constrained by radiometric dating, offers the best framework for understanding the development of non-glaciated landscapes in western Europe.