Neotectonic faulting and the Late Weichselian shoreline gradients in SW Norway |
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Authors: | Stein Kjetil Helle Noralf Rye Bjrg Stabell Lisbeth Prsch-Danielsen Christer Hoel |
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Institution: | aDepartment of Earth Science, University of Bergen, Allégt. 41, N-5007 Bergen, Norway;bDepartment of Geosciences, University of Oslo, P.O. Box 1047, Blindern, N-0316 Oslo, Norway;cMuseum of Archaeology, Stavanger, P.O. Box 478, N-4001 Stavanger, Norway;dM-I Norge AS, Gamle Forusvei 43, N-4033 Stavanger, Norway |
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Abstract: | The Younger Dryas (YD) maximum highstand shoreline in SW Norway has traditionally been considered as being slightly concave, gradually steepening in the direction of uplift. This phenomenon is attributed to geoidal and isostatic effects near the former ice-sheet margin. On the basis of isolation basin data from the region, we have reconstructed this shoreline, and a Bølling-Allerød (B-A) lowstand shoreline, along three profiles in SW Norway. Along all profiles there are shore levels which, within the error limits estimated, cannot be captured by a single straight (or curved) shoreline. The anomalous shore levels occur near major fault zones and are interpreted to reflect differential uplift rates on opposite sides of faults, superimposed on the general glacio-isostatic tilting of the region. The inferred faulting is consistent with observations previously reported as neotectonic ‘claims’ in the region and shed new light on the deformational structures observed in seismic profiles of the fjord sediments. Excluding the anomalous shore levels, a straight shoreline with gradient ca. 1.1 m/km provides the best and most consistent representation of the YD shore levels along the three profiles. The B-A lowstand shoreline is constrained by fewer data points, but is approximately parallel-dipping the highstand shoreline. Our reconstructions imply a less steep YD maximum highstand shoreline compared to previous reconstructions, where gradients up to 1.4 m/km have been inferred. This may imply that the ice load effect on the lithosphere in SW Norway during the YD is less than previously assumed. |
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Keywords: | Neotectonic faulting Shoreline gradients Isostasy Younger Dryas Isolation basins SW Norway |
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