Discussion Reply to discussion of Gabrielsen et al. (2010) by Nielsen et al. (this volume): Latest Caledonian to present tectonomorphological development of southern Norway Roy H. Gabrielsen a, d, * , Jan Inge Faleide a , Christophe Pascal b , Alvar Braathen c, d , Johan Petter Nystuen a , Bernd Etzelmuller a , Sejal O'Donnell a a Department of Geoscience, University of Oslo, Oslo 0136, Norway b The Geological Survey of Norway (NGU), Trondheim, Norway c The University Centre in Svalbard (UNIS), Longyearbyen, Norway d Center of Integrated Petroleum Research, University of Bergen, Norway article info Article history: Received 2 February 2010 Accepted 5 February 2010 Available online 19 February 2010 Although important for understanding the tectono-sedimentary pattern and the associated “source-to-sink”-mechanisms of the Late PalaeozoicePresent development of the Norwegian conti- nental shelf, it is recognized among workers at the Norwegian shelf and the Norwegian mainland that the post-Caledonian uplift and erosion are processes not well constrained by geological data. In two recent contributions (Gabrielsen et al., 2005, 2010), attempts have been made to illustrate the geological complexity of the problem and also to define some crucial geological datasets that can be utilized better to understand this complexity. We, therefore, appreciate the attention the problem recently has received by workers testing new concepts and methods (Rohrman et al., 1995; Hendriks and Redfield, 2005; Nielsen et al., 2009a) and the debate following these contributions (Japsen et al., 2006; Lidmar- Bergström and Bonow, 2009; Nielsen et al., 2009b). Following the electronic publication of our most recent publication on the post- Caledonian uplift of southern Norway (Gabrielsen et al., 2010), Nielsen et al. (this volume) have pointed to several aspects in our paper that may need clarification. In their recent contribution (Nielsen et al., 2009a) and in the ongoing debate (Nielsen et al., 2009b; Lidmar-Bergström and Bonow, 2009), Nielsen et al. have forcefully advocated the so- called “glacial buzzsaw”-model (Brozovic et al., 1997; Mitchell and Montgomery, 2006) as the dominant force behind the origin and development of the smooth and low-relief topography characterizing the paleic surfaces in western Scandinavia. The glacial buzzsaw mechanism for the formation of low-relief topo- graphic landforms includes freeze-thaw processes, suggesting that (Alpine) glacial erosion, rather than tectonic uplift rates and lithologies limits mountain heights. This process has undoubtedly operated in the mountain regions of Scandinavia since onset of the present antigreenhouse climate for about 3e4 million years ago, and may also have been effective at the time when the Scandina- vian Caledonian mountain chain was at its maximum elevation in the late Caledonian stage. However, in our view, the glacial buzzsaw mechanism cannot alone account for the widely extensive paleic surfaces, originally grading towards sea level. The paleic surfaces are present in all parts of Scandinavia and are preserved at various elevations above present sea level (e.g., Riis, 1996; Lidmar- Bergström, 1999; Lidmar-Bergström et al., 2000; Etzelmüller et al., 2007) and the origin, age and present position of paleic surfaces are crucial for the discussion of the post-Caledonian relief development of South Norway. The paleic surfaces are not unam- biguously dated and the older of these may, in principle, have formed during a long time interval, between the end of the Cale- donian Orogeny and onset of the first mountain glaciers in the latest Cenozoic. However, based on the knowledge of the glaciation history of Scandinavia from Devonian to Present, we find the glacial buzzsaw mechanism problematic as a sole explanation for the topographic development of South Norway except for the last 3e4 Ma years of antigreenhouse climate, since it is difficult to substantiate that such mechanisms were actively and continuously promoting erosion and bulk uplift of the land over the time period in question. * Corresponding author. E-mail address: r.h.gabrielsen@geo.uio.no (R.H. Gabrielsen). Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo 0264-8172/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpetgeo.2010.02.003 Marine and Petroleum Geology 27 (2010) 1290e1295