The age and origin of Neoglacial moraines in Jotunheimen, southern Norway: new evidence from weathering‐based data

Abstract

This paper considers the controversial issue of the existence of pre‐‘Little Ice Age’ Neoglacial moraines in southern Norway. Schmidt hammer rebound values are combined with measures of boulder roundness and weathering rind thickness in an attempt to isolate moraines that include weathered boulders. A critical approach is used in distinguishing sites where boulders have weathered in situ from those where previously weathered clasts have been incorporated into relatively young moraines. The results confirm that possible pre‐‘Little Ice Age’ Neoglacial moraines seem to be restricted to small, high‐altitude glaciers in eastern Jotunheimen. It is concluded that at these glaciers a particularly large response to a short‐lived earlier Holocene climatic event is more likely to explain the survival of such moraines than a particularly subdued response to the climatic deterioration of the ‘Little Ice Age’. More refined dating techniques are required to determine the age of formation of the anomalous moraines, but before the palaeoclimatic significance of such dates can be assessed, a critical test is required to establish whether the moraines mark former ice‐front positions, and therefore reflect lowering of equilibrium line altitudes, or whether they have been displaced forwards by later and more extensive glacier advances.