Trimlines and Paleonunataks

Paleonunataks are mountain summits that remained above the surface of Pleistocene ice sheets and ice fields. Periglacial (or glacial) trimlines are weathering limits separating glacially eroded terrain on lower slopes from periglacial morphology on summits and plateaus. Trimlines were traditionally interpreted as representing the upper limits of former ice masses, but it is now established that many trimlines represent the transition zone between an upper zone of landforms preserved under cold-based glacier ice and a lower zone of glacial erosion. Approaches to the interpretation of trimlines include relative-age dating, surface exposure dating, geomorphological evidence, and paleoglaciological constraints.