A Younger Dryas moraine ridge and fjord delta in Valldal, Norddalsfjorden, Møre og Romsdal, Norway

Abstract

The fjords and valleys of Norway have been shaped during several glacial cycles of the Quaternary period. Subaquatic ridges that formed at or close to the grounding lines of glacier termini during stillstands or readvances within the last deglaciation are commonly found within the fjords. An example is a prominent moraine ridge representing a readvance of the Fennoscandian Ice Sheet during the Younger Dryas ( c. 12.9–11.5 ka BP) in Norddalsfjorden, More og Romsdal, Norway. Fjord deltas may form in the same setting at the mouths of tributary valleys or at fjord heads following deglaciation. They may grow to relatively large dimensions and have morphological features that reflect the dynamic environment that exists across the fluvial–marine transition. One such delta is located close to, and partly drapes, the proximal slope of the moraine ridge at Norddalsfjorden. Norddalsfjorden is a narrow (0.8–3.5 km wide) and relatively deep (up to about 500 m deep) fjord situated between high mountain peaks and intermittent valleys (Fig. 1). A transverse, subaquatic ridge is situated on a bedrock sill just SW of the Valldal tributary valley. High-resolution multibeam data clearly depict the ridge as a well-defined topographic high with an arcuate crest that is convex down-fjord (Fig. 1c). The crest of the ridge is c. …