Using LiDAR data to characterize and distinguish among different types of raised terraces in a fjord-valley setting

Abstract

Depositional terraces of diverse origin are common in Norwegian fjord valleys. They differ subtly morphologically and may be difficult to distinguish from one another without detailed field and stratigraphic investigation. We used LiDAR elevational data to describe previously identified glaciofluvial, glaciodeltaic, fluvial, and fluviodeltaic terraces in the Målselv valley, northern Norway, and show how they differ morphologically. Fluvial terraces are divided into two subtypes based on their difference in morphology. One type shows an undulating surface, often with a ridge-and-swale topography (scroll bars) associated with lateral accretion of moderate-to-high-sinuosity (meandering) channels, while the other shows remains of channels and braid bars associated with low-sinuosity channels. Fluviodeltaic terraces are generally flat and featureless, probably as a result of wave and tidal reworking of the terrace surface as it was raised above sea level. Glaciofluvial terraces show braided channel forms and occasional eolian dunes, while glaciodeltaic terraces are generally flat and featureless, in some cases having a moraine ridge on top and small beach ridges on the proximal, ice-contact slope. Terraces also show a distinct distribution pattern, with glaciofluvial and glaciodeltaic terraces graded to the marine limit occurring at higher elevations than fluviodeltaic and fluvial terraces. Based on the results presented here we show that a distinction can be made between different terraces based on morphological criteria revealed by LiDAR data. Such data should be acquired where possible to improve the quality of geomorphological mapping.

Keywords:

• LiDAR
• terraces
• fluvial
• glaciofluvial
• delta
• Quaternary
• Norway

Acknowledgments

Anders Romundset is gratefully acknowledged for making the authors aware of the existence and interpretational potential of the LiDAR data-set of the Målselv Valley. The reviews from John Jansen and an anonymous reviewer helped to clarify and improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.