ARTICLE IN PRESS Quaternary Science Reviews 23 (2004) 1391–1434 A review of postglacial emergence on Svalbard, Franz Josef Land and Novaya Zemlya, northern Eurasia S.L. Formana,*, D.J. Lubinskib, O.! Ingolfsson! c, J.J. Zeebergd, J.A. Snydere, M.J. Siegertf, G.G. Matishovg a Department of Earth and Environmental Sciences, University of Illinois, Chicago, IL 60607, USA b Institute of Arctic and Alpine Research, The University of Colorado, Boulder, CO 80309-0450, USA c Department of Geology and Geography, University of Iceland, Is-101 Reykjav!ık, Iceland d Netherlands Institute for Fisheries Research, Haringkade 1, P.O. Box 68 1970 AB IJmuiden, The Netherlands e Department of Geology, Bowling Green State University, Bowling Green, OH 43403, USA f Bristol Glaciology Centre, School of Geographical Sciences University of Bristol, University Road, Bristol BSS 1SS, UK g Murmansk Marine Biological Institute, 17 Vladimirskaya Street, Murmansk 183010, Russia Abstract The pattern of postglacial emergence in the Barents Sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern Eurasia. This review unites records of Holocene relative sea level from Svalbard, Franz Josef Land, and Novaya Zemlya to better understand the geometries of past ice sheet loads. Emergence data from northern Eurasia confine the maximum area of glacier loading to the northwestern Barents Sea, where >100 m of emergence is measured on Kongs^ya. Deglacial unloading commenced on western and northern Spitsbergen c. 13–12 14C ka ago, and by c. 10.5 14Cka on eastern Svalbard and more distal sites on Franz Josef Land and Novaya Zemlya. The marine limit phase (c. 13–12 14C ka) on western and northern Spitsbergen is characterized by the construction of spits indicating a dominance of long-shore drift over storm- generated fetch, reflecting extensive sea-ice coverage of coastal areas. At sites in proximity to the ice sheet margin on western and northern Spitsbergen there is evidence for a transgressive–regressive cycle c. 6–4 14C ka, possibly reflecting back migration of displaced mantle material. A modern transgression is inferred from the marine erosion of 17th century cultural features and 14C ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c. 2 to 1 ka ago. The greatest observed emergence on Franz Josef Land occurs on Bell Island, with a marine limit at 49 m aht, formed c. >10 14C ka. Available emergence data since 9 ka show rising strandlines toward the southwest at B0.3 m/km. The northern limit of emergence on Franz Josef Land is poorly constrained because relative sea-level data is sparse north of 80300N. In contrast to Svalbard and Franz Josef Land, the marine limit on northern Novaya Zemlya is only 10–15 m above high tide and formed between 6.5 and 5.0 14C ka when global sea level was stabilizing. All sites show little apparent emergence during the past 2 ka, with the youngest raised landforms at identical heights to storm beaches. This minimal glacio-isostatic signature on Novaya Zemlya and on Vaygach Island, where deglaciation commenced >10 ka ago, indicates ice sheet thicknesses of o1.5 km. The spatial variation in emergence for the Barents Sea indicates that western and northern Spitsbergen and Novaya Zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage (2–6 ka) and were probably not in isostatic equilibrium. In contrast, central and eastern Svalbard and southern Franz Josef Land were beneath a substantial ice load and probably sustained this load for c. 10 14C ka and achieved isostatic equilibrium. Isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets, but deviates substantial at the ice sheet margin or areas covered by thin ice, like Novaya Zemlya. r 2004 Published by Elsevier Ltd. 1. Introduction distribution of past ice-sheet loads and deglacial history (e.g. Andrews, 1970). Observations on postglacial The pattern of postglacial emergence for many areas emergence are also important for developing a better in the Northern Hemisphere is pivotal in assessing the understanding of the glacio-isostatic adjustment process and the constraining properties of the underlying *Corresponding author. Fax: +1-312-413-2279. solid earth (Peltier, 1974, 1998; Cathles, 1975; Clark E-mail address: [email protected] (S.L. Forman). et al., 1978). Recent refinements in models of mantle 0277-3791/$ - see front matter r 2004 Published by Elsevier Ltd. doi:10.1016/j.quascirev.2003.12.007 ARTICLE IN PRESS 1392 S.L. Forman et al. / Quaternary Science Reviews 23 (2004) 1391–1434 viscoelastic structure and an improved understanding of However, in areas where post-glacial emergence was the extent and chronology of the Laurentide, Fennos- modest (o50 m), relatively brief (100 s to 1000 s of candian and Antarctic ice sheets provide a basis for years) arrests in sea level or transgressive–regressive estimating variations in ice sheet thickness during the events (o2 m) have been documented, reflecting the last deglaciation (Clark et al., 1994; Peltier, 1994, 1996; interplay between eustasy, isostasy, and steric and non- Lambeck, 1995). These earth rheological models accom- steric changes in sea level (Hafsten, 1983; Svendsen and modate site-specific relative sea level and global eustatic Mangerud, 1987; Forman, 1990; Fletcher et al., 1993; records (Fairbanks, 1989) providing new insight into the Forman et al., 1996; M^ller et al., 2002). Changes in the balance between ice sheet volume and changes in global course of relative sea-level on an emerging coastline are sea level in the past c. 20,000 yr (Tushingham and identified as constructional (broad raised terrace) or an Peltier, 1991; Peltier, 1994, 1996). erosional (escarpment) landform in the raised-beach In the last two decades of the 20th century large sequence, reflecting the complex interaction between sea uncertainties persisted on the geometry of late Pleisto- level, sediment supply, slope and wave energy (e.g. cene ice sheets and ice caps over the shelf seas bordering Elfrink and Baldock, 2002). the Arctic Ocean. Reconstructions of Late Weichselian The elevation of raised beach landforms was deter- ice sheet extent in the Barents Sea region range from a mined with either a barometric altimeter with an error of contiguous marine-based ice sheet over much of the 1–2 m or by transit or level with a precision of 10–30 cm. European arctic (e.g. Peltier, 1994, 1996; Lambeck, However, the relief on any one raised beach is usually 1– 1995), to smaller, coalescent ice caps based on arctic 2 m, which limits precision in assessing past sea level. archipelagos (e.g. Lambeck, 1995; Siegert and Dowdes- The datum for measuring the elevations across a raised well, 1995; Siegert et al., 1999; Svendsen et al., 1999). strand plain is the present mean high tide mark (m aht), This past disparity in ice sheet reconstructions reflected which is easily discernable on most coastlines as a swash the paucity of field observations to constrain the extent, limit. Coastal areas in the Barents Sea are microtidal thickness, and timing of late Quaternary glacial events with o2 m between high and low tide (Proshutinsky in northern Eurasia. A critical field observation to et al., 2001). The storm beach elevation varies across the determine the magnitude and distribution of past-glacier area attaining heights of 1–2 m within inner fjords and loads and the timing of deglaciation is the altitude and increasing to 4+m on exposed rocky headlands and age of raised-beach deposits. Quantitative studies on areas exposed to direct storm fetch (Forman, 1990; Svalbard defining the pattern of post-glacial emergence Zeeberg et al., 2001). Driftage is often conveyed and timing of deglaciation have been pursued since the further inland and beyond the storm beach limit up late 1950s (e.g. Feyling-Hansen and Olsson, 1959; Blake, valleys with the reverse flow of river discharge during a 1961a; Salvigsen, 1978, 1981, 1984; Forman et al., 1987; storm surge. Landvik et al., 1987; Forman, 1990; Salvigsen et al., 1990; Bondevik et al., 1995; Forman and Ingolfsson,! 2000; Bruckner. et al., 2002). Starting in the early 1990s 3. Radiocarbon dating the large expanse of the Russian Arctic became accessible to international scientific expeditions provid- Radiocarbon dating of driftwood, whalebone, walrus ing new Quaternary geologic data on former ice sheets. bone, seaweed and shell from raised-marine sediments This review unites observations on Holocene relative sea provides age constraint on marine inundation and level history for Svalbard (Norway) and Franz Josef deglaciation. Driftwood is the preferential subfossil Land and Novaya Zemlya (Russia) to assess patterns of collected from the raised-beach sequences because of postglacial emergence for areas that were beneath the its suitability for 14C dating and close association with Barents Sea/Eurasian ice sheet (Fig. 1). paleo-sea level. Often, the outer rings of driftwood logs were sampled to obtain 14C ages in close association with the sea level depositional event. If driftwood was 2. Near-shore conditions and the raised beach record not located, then whalebone and walrus-skull bone were retrieved for 14C dating. Bones were usually sectioned by The present altitude of raised beaches in the Eurasian saw and an internal, well-preserved dense part of the north reflects principally two competing processes; the bone was submitted for 14C dating. The collagen- postglacial rise in global sea level and isostatic up dominated gelatin extract from each bone was dated, warping of the lithosphere with disintegration of the last which in previous Arctic studies has yielded accurate 14C ice sheet that mostly occupied the Barents Sea.