Characterization of De Geer moraines in Finland based on LiDAR DEM mapping

Abstract

The three-dimensional characteristics and interdistances of De Geer moraine ridges were measured at different localities in southern and western Finland. We used a geographical information system to investigate how accurately Light detection and ranging (LiDAR) based digital elevation models (DEMs) are able to record the appearance of these moraine features. The results indicate that LiDAR DEMs sensitively record the length, width, height, orientation and interdistances of De Geer moraines, whereas their detailed cross section is less well represented. Based on a total of 563 moraine ridges recorded in the present dataset from four primary study sites, De Geer moraines were found to be typically 50–300 m long, 10–20 m wide, 0.5–2 m high and individual ridges covering areas of 500–6000 m2, with considerable inter- and intrasite variability. Comparisons of the measured variables of De Geer moraines with their deposition environment suggest that the dimensional variables of ridges are less dependent on the depositional environment compared to ridge morphological features and interdistances. Measurements of interdistances recorded in the dataset are based on four primary and six secondary study sites. De Geer moraine interdistances are suggested to be due to a combination of the rapidity of ice margin recession, proglacial water depth and terrain topography. The longest interdistances and most complex De Geer moraine geomorphology were found in deep water (>200 m) proglacial environments.