The stratigraphy of the Ra-ridge, a marine terminal moraine of Younger Dryas age, was studied in two large gravel pits at Vister and Bjørnstad. Glaciofuvial sediments in foreset beds dominate. Till beds overlie the foreset beds, or they are interbedded with them. Several different processes were involved in the deposition of the tills, such as lodgement, melt-out and flow processes. All beds were deposited below sea level at or near a grounded glacier front. Phases when the glacier was located to the north (up glacier) of the moraine are represented by beds of fine-grained glaciomarine sediments. Folds and faults are evidences of an overriding and/or oscillating glacier front. The stratigraphy shows that the glacier front oscillated more during formation of the Ra-ridge at Vister than at Bjørnstad.
Stratigraphy and sedimentation of a terminal moraine deposited in a marine enviroment - two examples from the Ra-ridge in Østfold, southeast Norway