Modelling late Cenozoic isostatic elevation changes in Storfjorden, NW Barents Sea: an indication of varying erosional regimes F.A. Butt a, * , A. Elverhùi a , B.O. Hjelstuen b , P. Dimakis c , A. Solheim d a Department of Geology, University of Oslo, PO Box 1047, Blindern, N-0316 Oslo, Norway b Geoconsult, Geoconsult, Nedre Aastveit 12, N-5083 évre Ervik, Norway c Norwegian Water and Energy Administration NVE), Middelthuns gt. 29, PO Box 5091 Majorstua, N-0301, Oslo, Norway d Norwegian Geotechnical Institute NGI), PO Box 3930, Ullevaal Stadion, N-0806 Oslo, Norway Received 18 May 2000; accepted 26 March 2001 Abstract Storfjorden Fan off NW Barents Sea contains ,116 £ 10 3 km 3 of sediments which are interpreted to have been derived from a drainage area measuring 69 £ 10 3 km 2 during the last ca. 2.3 m.y. Published isopach maps of the Storfjorden deposits have been used in a numerical model to simulate late Cenozoic isostatic elevation changes in the Storfjorden drainage area. The volume estimates in the depositional area for various time intervals together with the corrected density estimates for the eroded sediments indicate that ,1100 m of sediments have been eroded from the drainage area during the past ca. 2.3 m.y. The results of isostatic modelling show three distinct topographic phases during this time: a subaerial phase 2.3±1.4 Ma), a transition phase 1.4±0.8 Ma) and a submarine phase 0.8 Ma±present). In addition, sediment yield values from the drainage area during various intervals have been calculated. Highest sediment yield values are obtained for the subaerial phase while those for the submerged phase are the lowest. The age estimates are somewhat uncertain, but based on the modelling results together with the estimates of sediment yield, it is suggested that the changes in elevation and sediment yield values can be linked to the documented late Cenozoic paleoclimatic shifts along the western Svalbard±Barents Sea Margin. The doubling of sediment yield in the 1.6±1.4 Ma time from the preceding 2.3±1.6 Ma interval, despite lower topography, is related to major ice expansion under a subaerial scenario. The lowest yield values during the past 0.8 m.y., despite repeated glacial advances, are attributed to submergence of the area below sea level such that periods of erosion were limited to peak glacials with negligible erosion during the intervening interstadials and interglacials. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Late Cenozoic paleoclimate; Topographic reconstruction; Barents Sea; Sediment yield; Isostatic modelling 1. Introduction Cenozoic uplift and erosion of the Barents Sea shelf has been proposed since the beginning of the 20th century Nansen, 1904, 1920). Subsequent studies have con®rmed this view Harland, 1969; Nùttvedt et al., 1988; Va Êgnes and Amundsen, 1993). Estimates of total Cenozoic erosion from different parts of the Barents Sea range from 500±3500 m with greatest erosion estimated for the northwestern parts Hjelstuen et al., 1996; Rasmussen and Fjeldskaar, 1996; Dimakis et al., 1998). A signi®cant part of this erosion took place during the late Cenozoic Eidvin and Riis, 1989). Based on the volume of eroded sediments seen off the present-day Storfjorden Trough, an erosion rate of almost 0.5 mm/year is estimated for NW Barents Sea during the last 3 m.y. Sedimentary Geology 143 2001) 71±89 0037-0738/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S0037-073801)00107-5 www.elsevier.com/locate/sedgeo * Corresponding author. Fax: 147-22-85-4215. E-mail address: f.a.butt@geologi.uio.no F.A. Butt).