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In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate.

The largest dune fields in Sweden and Norway are small in international comparison but still form distinct parts of this previously glaciated landscape. The dunes formed c.10.5-9 ka ago, shortly after the last deglaciation, when winds close to the ice sheet were strong and vegetation was largely absent [1-4]. Since then they have been more or less stable and today they are covered by forest. Most of the dunes are curvi-linear in shape and formed transverse to the wind [5]. Here we present a sedimentary model for these transverse inland dunes, based on geophysical and sedimentological investigations of dunes at Skattungheden, Bonäsheden and Starmoen in central Sweden and south-eastern Norway. Ground-penetrating radar profiles reveal the main architectural elements of the dunes, while logging of sediment exposures in the dunes provide information on sedimentary structures. Grain-size analysis and scanning electron microscope studies of individual grains give us more detail on sediment characteristics.The main dune body, consisting of cross beds generally dipping 25-30°, makes up the largest part of the dunes; minor elements include windward side cover, dune-crest superimposed features and dune-toe apron (Fig. 1). The dominating sediment structures are planar parallel lamination, massive to vaguely stratified beds and a few types of secondary structures, such as bioturbation or physical disturbances. Few large erosional discordances are seen, and the dominating depositional processes are wind-ripple migration and some grain fall on the sloping lee sides. The sediments are well-sorted fine-to-medium sand, dominated by quartz, but with significant amounts of feldspar as well as some lithic fragments, micas and heavy minerals. Most grains are angular to subrounded and their surfaces display few traces of aeolian transport. Overall, the dune sands show large similarities to their source material (glacifluvial deposits), which suggests only short transport and brief reworking by aeolian processes.References[1] Alexanderson, H. and M. Bernhardson, OSL dating and luminescence characteristics of aeolian deposits and their source material in Dalarna, central Sweden Boreas, 2016. 45: p. 876-893.[2] Alexanderson, H. and M. Henriksen, A short-lived aeolian event during the Early Holocene in southeastern Norway. Quaternary Geochronology, 2015. 30: p. 175-180.[3] Bernhardson, M. and H. Alexanderson, Early Holocene NW-W winds reconstructed from small dune fields, central Sweden. Boreas, 2018.[4] Alexanderson, H. and D. Fabel, Holocene chronology of the Brattforsheden delta and inland dune field, SW Sweden. Geochronometria, 2015. 42: p. 1-16.[5] Bernhardson, M. and H. Alexanderson, Early Holocene dune field development in Dalarna, central Sweden: A geomorphological and geophysical case study. Earth Surface Processes and Landforms, 2017. 42: p. 1847-1859.

During the course of this three-year project, we have studied aeolian deposits at 70 sites within sixteen areas in south-central Sweden. Inland dunes have been the focus, but some sites with coversand and coastal dunes have also been investigated. We have mapped dune morphology, mainly by LiDAR-based remote sensing, studied the internal sediment architecture by ground-penetrating radar profiling and in sediment exposures, documented the sedimentology of the deposits with field and laboratory methods as well as determined the age of the deposits with luminescence and radiocarbon dating. In this scientific report to the Geological Survey of Sweden, who funded the project, we present a summary of the project and its results. The largest and best developed dune fields are found at glacifluvial deposits in Värmland and Dalarna, while in areas south thereof there are mainly scattered dunes or coversand deposits. A range of dune types has been observed, but transverse dunes seem to be dominating and the majority of these are oriented roughly NE-SW. The bulk of the aeolian deposits were formed shortly after the local deglaciation and, once stabilised, do not appear to have been significantly reworked during the Holocene. Most Mid- and Late-Holocene aeolian deposits consist of coversand, apart from in coastal areas where e.g. young foredunes are found.Our results thus largely confirm the hypothesis of previous investigators but we do add a significant amount of new information. We provide, for the first time for most of our study areas, numerical ages for the aeolian deposits and thus provide the timing and duration of sand-drift events in south-central Sweden. The ages, in combination with detailed geomorphological mapping, allow us to distinguish phases of dune-field development, which are likely due to changes in wind patterns and vegetation cover, and also to correlate Swedish aeolian deposits to regional storminess periods. Based on sedimentological information we are able to reconstruct dominating depositional processes, transport paths and sediment sources. Additional outcomes of the project are e.g. methodological developments (LiDAR mapping, luminescence dating) and pilot studies of potential relevance for applied geology (coastal development).