Topo-climatic controls on rock glacier chronology since Lateglacial period in the northwestern part of Mattertal, Swiss Alps, reconstructed by TCN dating

Postglacial evolution of landscapes in the Alps have evolved under a combination of glacial, paraglacial and periglacial processes in response to climate change. This study aims to reconstruct the timing and activity of rock glaciers (RGs) since the Lateglacial period in five tributary catchments of Mattertal, Swiss Alps, based on 10 Be ages collected from relict, inactive and active RGs, roche moutonnées and moraines. These 10 Be ages show that the RGs followed different histories between and within the catchments depending on the size and elevation of the catchment, deglaciation history, aspect and slope. In low elevation catchments (top elevation ~2900 m a.s.l.) RGs developed already after Gschnitz cold stage (17–16 ka), but reduced debris supply from small rockwalls led to stabilization of the RGs before or during the Younger Dryas (YD). In middle elevation catchments (top elevation ~3200 m a.s.l.) large rock failures during the deglaciation after YD promoted rapid advances of RGs, which were stabilized in the early Holocene warm period or are still active in accordance with the elevation, aspect and debris supply. In high elevation catchments (top elevation ~3500 m a.s.l.) wide occupation of glaciers prevented an exposure of rockwalls over the postglacial period, resulting in the lack of RGs, but deglaciation on south-facing slopes in the early Holocene may have promoted the development of RGs that were later overridden by the LIA glaciers. These findings contribute to the discussion on the transition from deglaciation to RGs, or the future response of RGs to climate change.