The interpretation of geomorphological features has became easier with the use of Light Detection and Ranging (LiDAR) data. GTK researchers Drs. Ojala, and Palmu show applications of LiDAR on Quaternary research in Finland in their GTK’s Science Blog text.
The advent of LiDAR (Light Detection And Ranging) technology has enabled rapid documentation of geological and geomorphological characteristics and allowed significant advances in theories on these formations (e.g. Johnson et al., 2015). Previously detected mega-scale landforms, such as large drumlins and end moraine complexes, show up in LiDAR-based digital elevation models (DEM) in greater detail than ever before, and landforms that are smaller than resolved from topographic maps and 10 m grid DEMs can now be detected and examined using LiDAR DEMs (e.g. Johnson et al., 2015; Palmu et al., 2015). LiDAR provides significant advantages over aerial photographs in forested landscapes. High-resolution DEM imagery can be applied to study geological features such as glacial lineations (Greenwood et al., 2015; Eyles et al., 2016), De Geer moraines (e.g. Bouvier et al., 2015; Ojala et al., 2015; Ojala 2016), ribbed and hummocky moraines (e.g. Möller and Dowling, 2015), beach ridges, cliffs and shore terraces (e.g. Ojala et al., 2013), fluvial terraces, floods plains and lateral meltwater channels (e.g. Eilertsen et al., 2015), post-glacial fault scarps and landslides, and other sedimentary features related to paleoseismic activity (e.g. Sutinen et al., 2014; Mikko et al., 2015; Palmu et al., 2015), and lineaments, fracture and fissure features of bedrock (e.g. Scheiber et al., 2015; Skyttä et al., 2015) (Fig. 1), among many others (e.g. Johnson et al., 2015).
The availability of LiDAR DEMs has changed the procedure of Quaternary mapping from the registering of superficial sediment types to thematic glaciodynamic mapping with classification of glacigenic deposits in Scandinavia (e.g. Putkinen et al., 2016). The experience gained thus far indicates that LiDAR data have substantially enhanced the usefulness of the previously mapped areas. It has also been demonstrated that Quaternary mapping with LiDAR remote sensing has considerably reduced the amount of expensive field work and the mapping time in general, thus proving an indispensable tool that is both convenient and cost-effective.
The recent work at the Geological Survey of Finland (GTK) by Ojala et al. (2013), Ojala et al. (2015), Ojala (2016), Palmu et al. (2015), and Sutinen et al. (2014) has focused on using LiDAR technology in the construction of ancient shorelines, the mapping and characterization of De Geer moraines, and the detection and classification of post-glacial fault scarps and seismically-induced landforms in Finland. Ojala et al. (2013) compiled an ancient shoreline geodatabase (ASD) to systematically classify and model shoreline displacement during the Litorina Sea maximum extension and the highest shoreline. They utilized LiDAR DEMs in validating all the old observations made since the beginning of the 20th century and created new data points for areas that were lacking information. The compiled ASD and shoreline reconstructions are available through the Hakku spatial product service (http://hakku.gtk.fi/) and the Maankamara map service interface (http://gtkdata.gtk.fi/Maankamara) provided by GTK. The relative altitude of the shoreline in the past contributed to the depositional environment of the superficial deposits in Finland, which is why knowledge of shoreline displacement over time, is important when mapping Quaternary deposits and searching for raw materials such as groundwater, gravel, sand or clay for industry and public use.
Ojala et al. (2015) and Ojala (2016) demonstrated that LiDAR-based DEMs capture the dimensions and characteristics of De Geer moraines (DGM) efficiently and accurately, and provide an opportunity to enhance reconstruction of the dynamic behavior of the Fennoscandian Ice Sheet (FIS) through the last glacial cycle. DGM ridges (Fig. 2) are known to indicate the location, curvature, and direction of the retreating ice margin during deglaciation. With systematic LiDAR DEM screening and mapping of DGMs, Ojala (2016) showed that their regional distribution is more widespread in Finland than previously presented. By comparing DMG interdistances with Sauramo’s (1923) varved clay chronology, Ojala (2016) concluded that an annual cycle is involved in the De Geer ridge-forming process and that regular and evenly spaced De Geer ridges probably represent the local rate of ice-margin retreat, or at least are very close to it. However, because of their heterogenic appearance and site-specific variations in the local climate and glacial dynamics they cannot be taken as reflecting the annual rhythm of deglaciation sensu stricto. Ojala (2016) also demonstrated that a clear relationship exists between proglacial water depth and DGM interdistance where longer interdistances are related to deeper water in the proglacial basins, which has a clear importance from the dynamic perspective of glacier retreat.
Palmu et al. (2015) have created a growing database of previously known and published post-glacial faults (PGF), paleolandslides and other morphological features of Quaternary deposits related to post- and late-glacial seismic activity in Finland. Their approach is based on a systematic search for (screening) and mapping of these features using ArcGIS-based (©ESRI) spatial tools and remote sensing. They have shown that LiDAR DEMs are exceptionally useful when searching for, delineating and measuring the scarp height variability of PGFs and morphological parameters of landslide. Their work also includes field reconnaissance of potential PGFs with ground penetrating radar, drillings, and trenching, which is currently ongoing.
Greenwood, S.L., Clason, C.C., Mikko, H., Nyberg, J., Peterson, G., Smith, C.A., 2015. Integrated use of LiDAR and multibeam bathymetry reveals onset of ice streaming in the northern Bothnian Sea. GFF 137, 284–292.
Möller, P, Dowling, D.P.F., 2015. The importance of thermal boundary transitions on glacial geomorphology; mapping of ribbed/hummocky moraine and streamlined terrain from LiDAR, over Småland, South Sweden. GFF 137, 252–284.
Ojala, A.E.K., Palmu, J.-P, Åberg, A., Åberg, S. & Virkki, H., 2013. Development of an ancient shoreline database to reconstruct the Litorina Sea maximum extension and the highest shoreline of the Baltic Sea basin in Finland. Bulletin of the Geological Society of Finland 85, 127–144.
Palmu, J.-P., Ojala, A.E.K., Ruskeeniemi, T., Sutinen, R. & Mattila, J., 2015. LiDAR DEM detection and classification of postglacial faults and seismically-induced landforms in Finland: a paleoseismic database. GFF 137, 344–352.
Putkinen, S., Putkinen, N., Sarala, P., Palmu, J.-P., Ojala, A.E.K. & Ahtonen, N., 2016. Map database of superficial deposits and glaciodynamic features in Finland − methodology and classifications. 32nd Nordic Geological Winter Meeting, Helsinki, Finland, 13-15 January 2016. Bulletin of the Geological Society of Finland, Special volume, pp. 310.
Sauramo, M., 1923: Studies on the Quaternary varve sediments in southern Finland. Bulletin de la Commission ge´ologique de Finlande 60, 164 pp.
Scheiber, T., Fredin, O., Viola, G., Jarna, A., Gasser, D., Łapińska-Viola, R. Manual extraction of bedrock lineaments from high-resolution LiDAR data: methodological bias and human perception. GFF 137, 362–372.
Skyttä, P., Kinnunen, J., Palmu, J.-P., 2015. Korkka-Niemi, K., Bedrock structures controlling the spatial occurrence and geometry of 1.8 Ga younger glacifluvial deposits—Example from First Salpausselkä, southern Finland. Global and Planetary Change 135, 66–82.
Teksti: Antti Ojala
Dr. Antti E.K. Ojala from the Geological Survey of Finland participated the research team and was funded by the Academy of Finland (QUAL-project, grant #259343). Antti is a geologist with a wide experience on aquatic sedimentation processes, micro-structure sedimentology and dating of sediments with varves, radiometric and palaeomagnetic methods. He has led and participated in several international research projects related to aquatic environments and climate change. His recent QUAL project deals with quantitative Holocene climate variability in Southern Svalbard.
Antti E.K. Ojala
Geological Survey of Finland
tel: +358 40 8489796
Teksti: Jukka-Pekka Palmu
PhD Jukka-Pekka Palmu is a geologist and senior specialist with a wide experience on glacial and Quaternary geology, sedimentology, engineering geology, hydrogeology, and GIS. He has led and participated in several multidisciplinary research projects related to Quaternary geological mapping, aggregate resources investigations, geological map databases, hydrogeology, geodiversity and land use planning.