Ice sheet erosional impacts in the low-relief shield terrain of northern Fennoscandia
2014 (English)In: 44th international Arctic Workshop, Program & Abstracts 2014. Institute of Arctic and Alpine Research (INSTAAR), University of Colorado at Boulder, 131 pp., 2014, 42- p.Conference paper, Abstract (Refereed)
Much previous work on Late Cenozoic glacial erosion patterns in bedrock has focussed on mountain areas. We here identify varying impacts of ice sheet erosion on the low-relief bedrock surface of the Fennoscandian shield, and examine the geological, topographical and glaciological controls on these patterns.
We combine GIS-mapping of topographical, hydrological and weathering data with field observations. We identify and investigate areas with similar geology and general low relief that show different degrees of ice sheet erosional impact, despite similar ice cover histories. On two transects with a total area of ~84 000km2 across the northern Fennoscandian shield, we first establish patterns of glacial erosion and then examine why glacially streamlined areas exist adjacent to areas of negligible glacial erosion. The northern transect includes two areas of exceptional glacial preservation, the Parkajoki area in Sweden and the so-called ice divide zone in Finland, each of which preserve tors and deep saprolite covers. The southern transect, overlapping in the northern part with the first transect, includes areas of intense glacial streamlining, with bedrock areas stripped of loose material and barely any weathering remnants.
For both areas, we firstly present the indicators we have availabe for ice sheet erosional impact: streamlined and non-streamlined inselbergs; parallel and dendritic/rectangular drainage patterns; the absence and presence of Neogene weathering remnants. This is followed by an investigation of factors that possibly influence ice sheet erosional impact: (pre-glacial) land surface elevation and topography, bedrock type and structure, and the ice cover history.
We find that the extreme preservation of pre-glacial relief in certain parts of the study area is likely explained by repeatedly divergent flow and frozen-based conditions, and that the most likely control causing glacial streamlining and strong erosion was acceleration of flow around major obstacles and convergence towards major bed depressions. No direct impact of rock type on glacial erosion patterns was found, but an indirect control appears clear. Bedrock geology and long-term differential weathering and tectonic evolution determined the topography of the pre-glacial landscape, and these topographic differences subsequently influenced ice sheet dynamics and thereby partly controlled ice sheet erosion on the Northern Fennoscandian shield.
Place, publisher, year, edition, pages
2014. 42- p.
IdentifiersURN: urn:nbn:se:su:diva-102264OAI: oai:DiVA.org:su-102264DiVA: diva2:708918
44th international Arctic Workshop, 15-16 March 2014, Institute of Arctic and Alpine Research (INSTAAR), University of Colorado at Boulder, US