Linear Till Ridges in the Southern Norwegian-Swedish Mountains—Evidence for a Subglacial Origin

Abstract

An uncommon type of narrow till ridge occurring within a limited area in the southern Swedish mountains is examined. The ridges are located high on gentle mountains slopes and usually have a very orderly appearance, with zig-zag patterns and straight sections. Excavations in two ridge systems revealed a homogenous till without sorted material or sedimentary structures. The stratigraphy and morphology indicate that the ridges were created by squeezing of till into subglacial voids, at some localities most likely related to subglacial drainage networks. The ridges have no clear relationships to deglaciation landforms in the area. At one locality some ridges are partially destroyed by fluting interpreted to predate the deglaciation phase. One possible explanation for the preservation of the ridges is that they were created before the last phase of deglaciation and were preserved under cold-based ice.