Deciphering Late Cenozoic development of the western Svalbard Margin from ODP Site 986 results F.A. Butt a, * , A. Elverhøi a , A. Solheim b , C.F. Forsberg c a Department of Geology, University of Oslo, P.O. Box 1047, Blindern, N-0316 Oslo, Norway b Norwegian Geotechnical Institute, P.O. Box 3930, Ulleva ˚l Stadion, N-0806 Oslo, Norway c Norwegian Polar Institute, Polarmiljøsenteret, N-9296 Tromsø, Norway Received 1 June 1999; accepted 30 May 2000 Abstract The present work is based on sedimentological data from ODP Site 986 drilled off western Svalbard. The data include grain- size distribution, bulk mineralogy, clay mineralogy, total carbon, total organic carbon and carbonate determinations from over 500 samples. The results show interesting trends across the seismic sequence boundaries defined earlier and can be related to changes in climate and depositional styles. The interpretation of these results together with the seismic observations and interpretations made earlier have shed new light on the timing of the onset of major glaciations and sedimentary processes on the Svalbard Margin during Plio-Pleistocene. The estimate for the timing of the first major glacial advance is revised to 1.6 Ma from the earlier estimate of 2.3 Ma. Barents Sea was the likely source for the sediments in the 2.3–1.6 Ma interval followed by Svalbard as the main sediment source in the post-1.6 Ma interval. It is also suggested that in view of their morphology and proposed sedimentary processes the sedimentary wedges off Svalbard–Barents Sea Margin are better described as slope aprons than in terms of ‘glacial fans’ or ‘trough mouth fans’ used earlier in the literature.  2000 Elsevier Science B.V. All rights reserved. Keywords: Svalbard; Barents Sea; Palaeoclimate; Depositional environment; Ocean drilling program 1. Introduction The western Svalbard–Barents Sea Margin has served as a key area for the studies of high latitude continental margins. The present study is based on sedimentological data from Ocean Drilling Program (ODP) Site 986 drilled during Leg 162 on the western Svalbard Margin between the Bellsund and Isfjorden fans (Fig. 1). Over 500 samples have been analysed for grain size distribution, bulk and clay mineralogy, TC, TOC and carbonate. The results provide a frame- work for a detailed study of Plio-Pleistocene deposi- tional environments and sedimentary processes. The objectives of the study are: 1. To estimate the timing of the onset of major glacia- tions on Svalbard. 2. To study the depositional environments and processes that have been active along the margin during the Plio-Pleistocene. The Late Cenozoic development of the margin has been extensively discussed earlier by, among others, Vorren et al. (1988, 1989, 1998), Faleide et al. (1996) and Solheim et al. (1996, 1998) based on seismic data. Marine Geology 169 (2000) 373–390 0025-3227/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0025-3227(00)00088-8 www.elsevier.nl/locate/margeo * Corresponding author. Fax: +47-22-85-4215. E-mail address: f.a.butt@geologi.uio.no (F.A. Butt).