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  • 1.
    Ebert, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hall, Adrian M.
    School of GeoSciences, University of Edinburgh, Edinburgh, UK.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Multi-phase development of a glaciated inselberg landscapeManuscript (preprint) (Refereed)
    Abstract [en]

    We investigate the evolution of a glaciated inselberg landscape in northern Sweden since the late Mesozoic, c. 65 million years ago. The study area is part of the Fennoscandian shield and has been stripped of cover rocks and also largely of weathering mantles by preglacial and glacial erosion to leave low relief inselberg plains, with a thin cover of Quaternary deposits. We use these inselbergs as the basis for study of the impact of glacial and preglacial erosion on the shield landscape. GIS-analyses of digital elevation models (DEMs) enable us to identify the morphometry of the inselbergs. Field mapping and mechanical excavations of inselberg margins allow links to be explored between dome-like granite inselbergs and sheet structures and to examine till and saprolite mantles. Very low glacial erosion in the Parkajoki area allows the final stages of preglacial relief development to be reconstructed for the Late Neogene. The hypsometry of the study area, in combination with inselberg elevation and distribution, allows four palaeosurfaces to be identified.

     

    The effects of glacial erosion on the bedrock forms of the inselbergs of the study area were generally restricted to inselberg streamlining by steepening of inselberg flanks. The inselberg landscape relief was enhanced by the removal of saprolite mantles during the Quaternary glaciations. The saprolites formed during the late Neogene, thin or absent close to the inselberg summits and of 10-20 m thickness at the inselberg feet and on the plains. The inselbergs are much older features, however, and deep kaolinization and soft ores are evidence for development by etching from a Mesozoic base level surface. Eocene marine clays on the continuation of the inselberg plains in northern Finland at around 260 m a.s.l. indicate that the inselberg plains above the Pakko palaeosurface generation predate the Paleogene-Eocene thermal maximum. Erosion rates, calculated for two reconstructed summit envelope surfaces, range between 1.5m/Myr and 4.8m/Myr since the late Mesozoic. The inselberg plains of northern Sweden are therefore directly comparable to other shield landscapes in extra-glacial areas that have experienced episodes of deposition of thin cover rocks, long periods of weathering and very low long term rates of erosion.

  • 2.
    Ebert, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    DEM-analysis of palaeosurface remnants in the mountain zone of northern SwedenManuscript (preprint) (Refereed)
    Abstract [en]

    Palaeosurface remnants are parts of old planation surfaces that have been elevated and partly down-cut by subsequent erosion. Such surfaces constitute an important landscape element when reconstructing the evolution of a landscape’s tong term development, although their morphological identification may be uncertain. In this study we examine to which degree palaeosurface remnants and surface generations can be identified objectively by GIS-analyses. A combination of fieldwork and GIS-analysis of digital elevation models (DEMs) was used to investigate palaeosurface remnants in two study areas, Ätnajåkki valley and Tjeuralako plateau in the northern Scandes of Sweden.

    Our results indicate that surfaces with an inclination of less than 11 °, and that were not affected by glacial erosion, correspond well with palaeosurface remnants as mapped subjectively in the DEM, air photos and in the field. Peaks in the hypsographic curves, at similar elevation intervals for both areas, show the altitudinal distribution of several palaeosurface generations that were identified in the field.

    The DEM analysis is shown to be a useful tool, but subjective mapping of glacially eroded areas is necessary to exclude glacially eroded areas, some of which may otherwise be misinterpreted as palaeosurface remnants, in the DEM. Hence, the combination of field observations and GIS-analyses is important when mapping and analysing palaeosurface remnants and their distribution correctly in a DEM. The method shown is nonetheless straightforward and reproducible.

  • 3.
    Ebert, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hall, Adrian M.
    University of Edinburgh, UK.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    DEM identification of macroscale stepped relief in arctic northern Sweden2011In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 132, no 3-4, 339-350 p.Article in journal (Refereed)
    Abstract [en]

    Stepped relief is a characteristic feature of many upland areas on Earth. In this study, we examine if stepped relief can be identified objectively by GIS-analysis of digital elevation models (DEMs). We specifically study the stepped relief landscapes of northern Sweden, comprising areas of contrasting topography in the mountainous northern Scandes and on the inselberg plains of the Precambrian basement east of the Caledonides.We mainly use hypsographic curves to examine the elevation distribution of the study areas and to identify palaeosurfaces. Peaks in the hypsographic curves are interpreted as palaeosurfaces, while hypsographic minima are interpreted as breaks in slope, separating these surfaces. In the northern Scandes, where only patchy remnants of palaeosurfaces remain, we use empirical cutoff values of slope angles to restrict palaeosurface areas to those identified in thefield and in air photos. In addition, air photo andfield mapping of glacially eroded areas is necessary to exclude glacially formed low relief surfaces, such as valley floors. These latter procedures introduce an unavoidable degree of subjectivity to the study. Our results indicate that in the northern Scandes, surfaces with an inclination of 11°, after glacially formed features are abstracted, correspond well with palaeosurface remnants. Breaks in slope separating the surface generations in themountains are centred around 860, 1320, and 1520 masl (above sea level), respectively. On the plains east of the northern Scandes, hypsographic data were filtered to remove inselbergs in order to analyse only the plains. Hypsographic curves of both the filtered and the unfiltered data of the inselberg plains show minima at elevations that correspond to steps separating multiple palaeosurfaces at elevations of 190, 250, and 400 masl. The steps separating the different palaeosurfaces are, in places, aligned with known geological discontinuities, but extensive remnants also transect structure. The presence of stepped relief is consistent with existing models of phased Cenozoic uplift and incision in northern Fennoscandia.

  • 4.
    Jakobsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Björck, Svante
    Alm, Göran
    Department of Physical Geography and Quaternary Geology.
    Andrén, Thomas
    Lindeberg, Greger
    Svensson, Nils Olov
    Reconstructing the Younger Dryas ice dammed lake in the Baltic Basin: Bathymetry, area and volume2007In: Global and Planetary Change, Vol. 57, 355-370 p.Article in journal (Refereed)
    Abstract [en]

    A digital 3D-reconstruction of the Baltic Ice Lake's (BIL) configuration during the termination of the Younger Dryas cold phase (ca. 11700 cal. yr BP) was compiled using a combined bathymetric–topographic Digital Terrain Model (DTM), Scandinavian ice sheet limits, Baltic Sea Holocene bottom sediment thickness information, and a paleoshoreline database maintained at the Lund University. The bathymetric–topographic DTM, assembled from publicly available data sets, has a resolution of 500×500 m on Lambert Azimuthal Equal Area projection allowing area and volume calculations of the BIL to be made with an unprecedented accuracy. When the damming Scandinavian ice sheet margin eventually retreated north of Mount Billingen, the high point in terrain of Southern central Sweden bordering to lower terrain further to the north, the BIL was catastrophically drained resulting in a 25 m drop of the lake level. With our digital reconstruction, we estimate that approximately 7800 km3 of water drained during this event

    and that the ice dammed lake area was reduced by ca. 18%. Building on previous results suggesting drainage over 1 to 2 years, our lake volume calculations imply that the freshwater flux to the contemporaneous sea in the west was between about 0.12 and 0.25 Sv. The BIL reconstruction provides new detailed information on the paleogeography in the area of southern Scandinavia, both before and after the drainage event, with implications for interpretations of geological records concerning the post-glacial environmental development.

  • 5.
    Jansson, Krister
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dahlgren, T.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    GIS modelling of the MIS 2-8 onshore glacial erosional pattern in northern Scandinavia2007In: Quaternary International, 2007Conference paper (Refereed)
    Abstract [en]

    A 50-m cell size digital elevation dataset over northern Scandinavia has been analysed for patterns of glacial erosion using filtering techniques of the Erdas Imagine 8.6

    spatial modeller software. A maximum value filtering technique using variable neighbourhoods has been applied such that existing highpoints in the landscape have been

    used as erosional base levels for the reconstruction of past landscape relief. We assume that the highest surfaces have experienced no down-wearing (or, alternatively, an

    even down-wearing could be specified) and also that the size of the valleys rather than the direction of the valleys relative to former ice flow directions determines how

    much material has been removed by ice sheet erosion. Over multiple runs the reconstructed paleo-relief becomes increasingly dominated by the highest summits in the

    landscape and the valley pattern is smoothed by in-filling from the sides. The model was run until eroded bedrock volumes equalled bedrock equivalents of erosion

    products deposited during MIS 2, 6, 8, 10, 12, 18 and for the full glacial period offshore of northern Norway. The pattern of glacial erosion, which is mainly correlated to

    slope angles and relative relief, is characterized by: (1) An abrupt start of glacial erosion below preserved summit areas; (2) Enhanced erosion in narrow valleys; (3)

    Restricted erosion of smooth areas, independently of elevation; (4) Erosion of small scale irregularities, and; (5) Restricted erosion on isolated hills in low-relief terrain.

  • 6.
    Jansson, Krister N.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dahlgren, K. I. Torbjörn
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glasser, Neil F.
    Goodfellow, Brad W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glacial erosion and the evolution of relief in northern Scandinavia over the last 2.7 Myr2008In: Geophysical Research Abstracts, Vol. 10, EGU2008-A-07548, 2008Conference paper (Refereed)
  • 7.
    Jansson, Krister
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dahlgren, K. I. T.
    Glasser, N. F.
    Goodfellow, B. W.
    Using a GIS filtering approach to replicate patterns of glacial erosion2011In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, no 3, 408-418 p.Article in journal (Refereed)
    Abstract [en]

    In order to extend our knowledge of glacial relief production in mountainous areas new methods are required for landscape reconstructions on a temporal resolution of a glacial cycle and a spatial resolution that includes the most important terrain components. A generic data set and a 50 m resolution digital elevation model over a study area in northern Sweden and Norway (the present day landscape data set) were employed to portray spatial patterns of erosion by reconstructing the landscape over successive cycles of glacial erosion. A maximum-value geographic information system (GIS) filtering technique using variable neighbourhoods was applied such that existing highpoints in the landscape were used as erosional anchor points for the reconstruction of past landscape topography. An inherent assumption, therefore, is that the highest surfaces have experienced insignificant down-wearing over the Quaternary. Over multiple reconstruction cycles, proceeding backwards in time, the highest summits increase in area, valleys become shallower, and the valley pattern becomes increasingly simplified as large valleys become in-filled from the sides. The sum of these changes reduces relief. The pattern of glacial erosion, which is to 60% correlated to slope angle and to 70% correlated to relative relief, is characterized by (i) an abrupt erosional boundary below preserved summit areas, (ii) enhanced erosion in narrow valleys, (iii) restricted erosion of smooth areas, independently of elevation, (iv) eradication of small-scale irregularities, (v) restricted erosion on isolated hills in low-relief terrain, and (vi) a valley widening independent of valley directions. The method outlined in this paper shows how basic GIS filtering techniques can mimic some of the observed patterns of glacial erosion and thereby help deduce the key controls on the processes that govern large-scale landscape evolution beneath ice sheets.

  • 8.
    Kleman, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    de Angelis, Hernán
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glasser, Neil
    Aberystwyth University.
    North American Ice Sheet build-up during the last glacial cycle, 115-21 kyr2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 17-18, 2036-2051 p.Article in journal (Refereed)
    Abstract [en]

    The last glacial maximum (LGM) outline and subsequent retreat pattern (21e7 kyr) of North Americanice sheets are reasonably well established. However, the evolution of the ice sheets during their build-upphase towards the LGM between 115 and 21 kyr has remained elusive, making it difficult to verifynumerical ice sheet models for this important time interval. In this paper we outline the pre-LGM icesheet evolution of the Laurentide and Cordilleran ice sheets by using glacial geological and geomorphologicalrecords to make a first-order reconstruction of ice sheet extent and flow pattern. We mappedthe entire area covered by the Laurentide and Cordilleran ice sheets in Landsat MSS images andapproximately 40% of this area in higher resolution Landsat ETMþ images. Mapping in aerial photographsadded further detail primarily in Quebec-Labrador, the Cordilleran region, and on Baffin Island.Our analysis includes the recognition of approximately 500 relative-age relationships from crosscuttinglineations. Together with previously published striae and till fabric data, these are used as the basis forrelative-age assignments of regional flow patterns. For the reconstruction of the most probable ice sheetevolution sequence we employ a stepwise inversion scheme with a clearly defined strategy for delineatingcoherent landforms swarms (reflecting flow direction and configuration), and linking these topreviously published constraints on relative and absolute chronology. Our results reveal that icedispersalcentres in Keewatin and Quebec were dynamically independent for most of pre-LGM time andthat a massive Quebec dispersal centre, rivalling the LGM in extent, existed at times when the SW sectorof the ice sheet had not yet developed. The oldest flow system in eastern Quebec-Labrador (Atlanticswarm had an ice divide closer to the Labrador coast than later configurations). A northern Keewatin-Central Arctic Ice Sheet existed prior to the LGM, but is poorly chronologically constrained. There is alsoevidence for older and more easterly Cordilleran Ice Sheet divide locations than those that prevailedduring the Late Wisconsinan. In terms of ice sheet build-up dynamics, it appears that “residual” ice capsafter warming phases may have played an important role. In particular, the location and size of remnantice masses at the end of major interstadials, i.e. OIS 5c and 5a, must have been critical for subsequentbuild-up patterns, because such remnant “uplands” may have fostered much more rapid ice sheetgrowth than what would have occurred on a fully deglaciated terrain. The ice-sheet configuration duringstadials would also be governed largely by the additional topography that such “residual” ice constitutesbecause of inherent mass balance-topography feedbacks.

  • 9. Napieralski, Jacob
    et al.
    Hubbard, Alun
    Li, Yingkui
    Harbor, Jon
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Towards a GIS assessment of numerical ice sheet model performance using geomorphological data2007In: Journal of Glaciology, Vol. 53, no 180, 71-83 p.Article in journal (Refereed)
    Abstract [en]

    A major difficulty in assimilating geomorphological information with ice-sheet models is the lack of a consistent methodology to systematically compare model output and field data. As an initial step in establishing a quantitative comparison methodology, automated proximity and conformity analysis (APCA) and automated flow direction analysis (AFDA) have been developed to assess the level of correspondence between modelled ice extent and ice-marginal features such as end moraines, as well as between modelled basal flow directions and palaeo-flow direction indicators, such as glacial lineations. To illustrate the potential of such an approach, an ensemble suite of 40 numerical simulations of the Fennoscandian ice sheet were compared to end moraines of the Last Glacial Maximum and the Younger Dryas and to glacial lineations in northern Sweden using APCA and AFDA. Model experiments evaluated in this manner were ranked according to level of correspondence. Such an approach holds considerable promise for optimizing the parameter space and coherence of ice-flow models by automated, quantitative assessment of multiple ensemble experiments against a database of geological or glaciological evidence.

  • 10.
    Risberg, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Isaksson, Mikael
    Arkeologikonsult.
    Alm, Göran
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Site location in the Stone Age landscape on the Södertörn peninsula, eastern middle Sweden: an ecological and economical approach2011In: Skrifter från Arkeologikonsult, ISSN ISBN 978-91-979352-0-3, no 1, 5-44 p.Article in journal (Other academic)
    Abstract [en]

    This paper aims to use GIS applications to interpret ecological and economical presumptions for the Stone Age habitation on the south-eastern part of the peninsula Södertörn, south of Stockholm, southeast Sweden. Specific questions concern how characteristic geographical features of the landscape have influenced the settlement sites before, during and after usage and how periods of continuity and discontinuity may be explained based on economical and ecological presumptions. The used data have been achieved from both geological and archaeological sources, such as the age of isolated lake basins and dates of sealed features like hearths and cooking pits. These have served as basis for the establishment of paleogeographical maps of the land/sea configuration at 6250, 5500, 4700 and 4000 BC constructed as tilted terrain models.

    It is concluded that the long-term occupation of the sites can be explained by their strategic location, which due to the steep topography was retained over extensive time periods. Their boundary positions have allowed a variety of resources to be exploited. Their location along waterways was convenient and efficient. If the results would render valid on a general scale, sites with a comparable function and patterns of use should be located along waterways in similar boundary zones. Such sites would probably have been settled as soon as suitable areas emerged from the sea and abandoned when the connectivity along the waterways seized.

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