In situ 10Be exposure ages from Norway: age-altitude diagrams

 

Linge, H1, Brook, E.J.2, Dahl, S.O.1,3, Mickelson, D.M.4, Nesje, A.1,5,

Raisbeck, G.M.5 and Yiou, F.5

 

1 Bjerknes Centre for Climate Research, Allégaten 55, N-5007 Bergen, Norway.

2 Department of Geosciences, Oregon State University, Corvallis, Oregon 97331, USA.

3 Department of Geography, University of Bergen, Breiviksveien 40, N-5045 Bergen, Norway.

4 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA

5 Department of Earth Sciences, University of Bergen, Allégaten 41, N-5007 Bergen, Norway.

6 Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bât 108, 91495 Orsay, France.

 

 

 

More than 150 10Be exposure ages have been obtained from various sites in Norway for the purpose of reconstructing Weichselian glacier geometry in time and space. Typically, glacially moulded surfaces below trimlines yield ages in the range 10 to 15 ka, i.e. the time elapsed since deglaciation, whereas exposure ages from bedrock outcrops and/or block surfaces in blockfields are in the range 25 to >80 ka. An additional trend is seen for mountain summits lacking evidence of glacial erosion; summit peaks highly exposed to weathering give younger ages than surfaces that have more shielded, near-summit elevations. However, old exposure ages are not unambiguous evidence for the existence of nunataks, and young ages are not necessarily synonymous with glacial erosion occurring during the Late Glacial Maximum (LGM); in both cases burial by cold-based, low-erosive ice may be of importance. More meaningful differences, possibly linked to thermal regimes and ice thicknesses, can be found in the general exposure age patterns between the western, eastern and northern regions.

            Recognizing that the Quaternary glacial history of Scandinavia is more complex than a glacial on-off signal, we seek to explore the Weichselian glacial history further by continued exposure dating activity. Whereas one of the overall aims is to reconstruct ice sheet configurations in the Weichselian period, 10Be exposure dating in addition offers information on subglacial conditions, subaerial weathering rates for various bedrock types, and duration of sediment/glacial burial when combined with a second cosmogenic isotope and/or with optically stimulated luminescence (OSL) dating.

 

 

 

Bjerknes Centenary 2004; Climate Change in High Latitudes, p 90-91, Bergen, Norway.

 

S Norway – (Gaustatoppen and Skorve) – reference no. 1

 

Eastern southern Norway – (Elgåhogna and Rendalssølen) – reference no. 1

W-E transect, southern Norway - reference 2 and 3

 

NW Norway, Romsdalsfjord – reference no. 4+5+6

 

W Norway, Ulvanosi –reference no. 7

 

N Norway, Nordland, W-E transect – reference no. 8

 

N Norway, Lofoten-Vesterålen – reference no. 9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References:

 

  1. Linge, H., Brook, E.J., Nesje, A., Raisbeck, G.M., Yiou, F. and Clark, H.A. (submitted QSR): In situ 10Be exposure ages from southeastern Norway: implications for the geometry of the Weichselian Scandinavian ice sheet.
  2. Brook, E.J., Nesje, A., Lehman, S.J., Raisbeck, G.M. and Yiou, F. (1996). Cosmogenic nuclide exposure ages along a vertical transect in western Norway: implications for the height of the Weichselian ice sheet. Geology 24, 207-210.
  3. Brook, E.J., Nesje, A., Lehman, S.J., Raisbeck, G.M. and Yiou, F. (in prep.). Exposure age constraints on the geometry and deglaciation of the Fennoscandian ice sheet.
  4. Bugge, B. (M.Sc. thesis in prep.). Advisor: Atle Nesje
  5. Hildreth, M.D. (2001). Surficial geology and late Weichselian ice sheet thickness at Skorgedalen, western Norway. M.Sc. thesis, University of Wisconsin, Madison, 73 p.
  6. Linge, H., Brook, E.J., Hildreth, M., Larsen, E., Mickelson, D.M., Nesje, A., Raisbeck, G.M., Yiou, F. (others??). Romsdalsfjord manuscript in prep.
  7. Diesen, M.G.B. (2003). Den vertikale isutbredelsen i Kvinnherad under siste istid. (Transl. The vertical ice extent in Kvinnherad during the last ice age). M.Sc. thesis, University of Bergen, 133 p.
  8. Linge, H., Brook, E.J., Darter, J.R., Mickelson, D.M., Olsen, L., Raisbeck, G.M., Yiou, F. (others??) (in prep.). Cosmogenic nuclide exposure ages from Nordland, northern Norway: coastal, fjord and inland data.
  9. Nesje, A., Brook, E.J., Dahl, S.O., Raisbeck, G.M., Yiou, F. (others?? Paasche?). Manuscript in prep. Lofoten-Vesterålen.
  10. Linge, H., Brook, E.J., Fjellanger, J., Raisbeck, G.M., Yiou, F. (others??). Pilot samples (11) from the Varanger Peninsula - to be measured autumn 2004.
  11. New project: Weichselian glaciation history of the ‘dry valleys’ of central Scandinavia. PI: Svein Olaf Dahl. Partners: Henriette Linge, Øyvind Lie, Anne-Grete Bøe Pytte, Edward J. Brook, Andrew Murray, Grant M. Raisbeck, Atle Nesje. Pilot samples (19) to be measured autumn 2004.