A Holocene lacustrine record of environmental change in northeastern Prince of , ,

KONRAD GAJEWSKI AND MONIQUE FRAPPIER

Gajewski, K. & Frappier, M. 2001 (December): A Holocene lacustrine record of environmenta l change in northeaster n Prince of Wales Island, Nunavut, Canada. Boreas, Vol. 30, pp. 285–289. Oslo. ISSN 0300-9483. A core from Prince of Wales Island in the central Canadian was analysed for pollen and sediment characteristics . From 9200 yr BP to 7000 yr BP, the landscape supported a pioneer vegetation under cold con- ditions, with relatively high sediment input to the lake. Between 7000 and 4000 yr BP there was a period of high pollen concentrations , more abundant Cyperaceae and Dryas on the landscape and Ž ner sediment input. In the last 4000 years, climate cooling is indicated. Konrad Gajewski (e-mail: [email protected] ) and Monique Frappier, Laboratory of Paleoclima- tology and Climatology, Department of Geography and Ottawa–Carleton Geoscience Centre, University of Ottawa, Ottawa, Ontario, K1N 6N5 Canada; received 8th January 2001, accepted 2nd April 2001.

Little is known about the postglacial vegetation history arctic ecological districts is found in the northern part of of large portions of the Canadian High Arctic. In the the Island, trending northwest–southeast between central arctic, pollen diagrams have been published only Ommanney Bay and Browne Bay (Woo & Zoltai 1977). from Somerset Island (Gajewski 1995). Pollen diagrams Prince of Wales Island was deglaciated from the are available from Banks Island (Gajewski et al. 2000) northwest to the southeast between approximately in the west, and Ellesmere (Hyva¨rinen 1985) and BafŽ n Islands to the east (e.g. Andrews et al. 1979; Jacobs et al. 1997; Mode 1997; Short et al. 1985; Williams et al. 1995). Holocene climate changes in the Canadian High Arctic have been interpreted from a variety of proxy- climate records (Ovenden 1988), including ice cores (e.g. Bourgeois et al. 2000; Fisher et al. 1995; Koerner & Fisher 1990) and fossil whalebone (Dyke et al. 1996b) or marine mollusc (Dyke et al. 1996a) distribu- tions. Results generally indicate warmer conditions in the early to mid-Holocene and cooling during the past several thousand years (Bradley 1990). Dyke et al. (1996b) suggest that ou ow from the melting ice sheets contributed to keeping the inter-island channels free of pack ice, and this would have contributed to maintain- ing these warmer conditions. A cooling in the late Holocene is noted from many regions, but the timing of this is not well established (Bradley 1990). We analysed a lake sediment core from a small lake on Prince of Wales Island in the central Canadian (Fig. 1). The purpose of this study is to document the Holocene environmental history of this part of the island and to determine if it was similar to that of nearby Somerset Island. The bedrock of Prince of Wales Island is primarily limestone or dolomite with a band of sandstone and conglomerate along the eastern side. The easternmost tip of the island, as well as , is Precambrian gneiss (Dyke et al. 1992). Highest vegetation cover is found on the eastern part of the island, in areas underlain by non-carbonate rock (Dyke Fig. 1. Map showing location of lake PWWL (informal name) on et al. 1992). The transition between the high- and mid- Prince of Wales Island. 286 Konrad Gajewski and Monique Frappier BOREAS 30 (2001)

Fig. 2. Sediment stratigraph y of core from lake PWWL.

11000 and 9000 yr BP (all ages are given in water interface. The top 4.5 cm of the interface was uncalibrated 14C yr BP). Most of the island was subsampled at the Ž eld station, and the remainder of the submerged following retreat of the ice and only uplands cores stored at 4°C in plastic wrap and aluminium foil. in the north and east remained above sea level (Dyke et In the laboratory, the cores were X-rayed on a GE al. 1992). The oldest dates of emergence are around DXD525 machine with Fuji Super HR-S 30 X-ray Ž lm. 10000 yr BP from and the northernmost Ninety 1-g wet samples were analysed for particle size part of Prince of Wales Island (Dyke et al. 1992). using a Malvern Mastersizer E with a 0.1–600 mm Site PWWL (73°34.5’N; 98°29.0’W; 110 m a.s.l.) is sample cell. Sample dispersion was achieved by the located in the Allen Lake region of northeastern Prince removal of organic material with hydrogen peroxide of Wales Island (Fig. 1). The underlying bedrock (29–32%) and the addition of 1–3 ml of sodium consists of conglomerate sandstone and siltstone (Woo pyrophosphate (10 g/l). One cm3 of sediment was & Zoltai 1977) and there are sandstones to the east and burned at 500°C for 3 h to estimate the organic content, carbonates to the west (Dyke et al. 1992). The region and another 3 h at 950°C to estimate the carbonate surrounding the lake was deglaciated between 10 000 content (Bengtsson & Enell 1986). and 9600 yr BP, but was submerged and a bone date of Four cm3 of sediment was processed for pollen using 9285 135 was reported from approximately the same standard methods (Faegri & Iversen 1975), including altitud§e as the lake (Dyke et al. 1992). Woo & Zoltai 10% HCl, hot 10% KOH, HF and acetolysis with Ž nal (1977) place the Allen Lake region in the High Arctic storage in silicon oil. Tablets of Lycopodium were vegetation zone, which is a polar desert characterized added prior to processing to enable the calculation of by sparse vegetation and low species richness. Locally, pollen concentration (Stockmarr 1971). Samples were the vegetation is relatively dense compared to typical also desegregated in warm sodium pyrophosphate and high arctic vegetation, and includes areas of peat passed through a 7-mm sieve to remove the clay-sized accumulation. A distinguishing feature of the vegetation particles. Pollen concentrations were very low and it immediately around the lake is an abundant population was difŽ cult to obtain sufŽ cient pollen sums. For each of Saxifraga oppositifolia. level, multiple slides were counted until (a) a sum of over 300 grains was achieved, (b) 10 slides were counted, or (c) there was no more material. Methods Cores were collected on 10 July 1995 in 4.3 m of water Results from an ice surface using a 5-cm diameter Livingstone corer. The uppermost section was cored in a clear The sediment consisted of 160 cm of inorganic lake plastic tube Ž tted with a piston to sample the sediment– sediment with several moss layers (Fig. 2). Mosses were BOREAS 30 (2001) Holocene environmental change, Canadian Arctic 287

Table 1. Uncalibrated radiocarbo n dates from lake PWWL.

Depth (cm) Age (yr BP) Lab number Moss

0.0–1.0 560 60 TO-7938 Scorpidium scorpioides (Hedw.) Limpr. 12.5–15.0 ¡1560 § 90 TO-7939 Drepanocladus group and Calliergon sp. 41.0–42.0 2600 § 80 TO-7940 Drepanocladus group 73.0–75.0 4140 § 80 TO-7941 Drepanocladus group and Calliergon sp 91.0–92.0 6480 § 140 TO-7942 Drepanocladus group and Calliergon sp. § also found embedded in the ice. Loss on ignition was Mosses submitted for dating are poorly preserved, but very low, remaining below 4% and decreasing to identiŽ cation revealed that they are characteristic of negligible levels below 100 cm (Fig. 2). Carbonate wetland environments. Scorpidium scorpioides (Hedw.) content, estimated by ignition at 950°C increased Limpr was present in every sample and constitutes the slightly below this level. sample collected from the surŽ cial sediment and lake Five samples of moss fragments were submitted for ice. This emergent and calciphile species grows in fens AMS radiocarbon dating (Table 1). The uppermost and bogs, or at the edges of lakes and ponds. The next sample was contaminated by bomb carbon and not used. most common component is aquatic and belongs to the Only the uppermost metre could be dated. The lower Drepanocladus group (possibly WarstorŽ a exannulatus sediment contained little organic matter, and, indeed, (Schimp. in B.S.G.) Loeske). Calliergon sp. fragments only two samples could be successfully counted for are also present in some of the samples. pollen from this sediment. Grain-size results were aggregated to present the

Fig. 3. Percentage pollen diagram from lake PWWL. Total pollen concentration (grains/ccm) based on all pollen excluding aquatics. 288 Konrad Gajewski and Monique Frappier BOREAS 30 (2001) relative volume size distribution of sand, silt and clay sediments (Gajewski 1995), and this was interpreted as (Fig. 2). In general, there is a relative increase in clays the time of maximum warmth. The high Poaceae and above 100 cm. Below 100 cm, silt is the most important Papaver pollen percentages along with low concentra- component of the sediment and the clay proportion tions and silty sediment suggests relatively colder decreases. Small peaks of over 20% sand are found conditions on Prince of Wales Island. A similar zone throughout the core. was found on , interpreted as a Pollen concentrations were low in the bottom of the re ection of pioneer vegetation by Hyva¨rinen (1985). core, in sediment corresponding to the lower organic This may help explain the higher silt content, due to matter, higher carbonate content, and higher silt more slopewash and sediment input into the lake. amounts. Concentrations increased before 6500 yr BP By 6500, Dryas and Cyperaceae pollen increased and and decreased again after 4000 yr BP (Fig. 3). the pollen concentrations increased nearly threefold. The percentage pollen diagram shows few changes The clay content increased, although there were still during the past 6500 years. Poaceae pollen was higher some peaks with relatively large sand amounts. Today, prior to 6500 yr BP, as was pollen of Papaver. pollen of Dryas and Cyperaceae is widely distributed, Cyperaceae and Saxifragaceae pollen decreased but is particularly abundant in the mid-arctic (Ritchie et between 3500 and 500 yr BP, when several other taxa, al. 1987). Pollen concentrations at Prince of Wales are notably Saxifraga oppositifolia, Brassicaceae and Poly- lower than on Banks Island, and it is doubtful that true podiaceae increased. Tree and shrub pollen, transported mid-arctic vegetation was growing around the site. from the low-arctic tundra and forests to the south After 4000 yr BP, Cyperaceae pollen decreased, remained more or less constant, except for a long-term while Poaceae, Saxifraga oppositifolia, Brassicaceae decrease in Betula pollen. and Ranunculaceae increased. These changes are slight, but suggest a cooling of the region, as these plants are characteristic of high-arctic vegetation. This cooling is Discussion seen elsewhere in the central arctic (Bradley 1990). There was no signiŽ cant change in the sediment at this Dating sedimentary sequences is difŽ cult in the arctic time. due to low organic content of most lake sediments, The pollen diagram from PWWL on Prince of Wales presence of Tertiary coal deposits in some regions and Island does not show large changes in the Holocene as extensive carbonate bedrock in the region (Gajewski et was also observed on Somerset Island (Gajewski 1995). al. 1995). With the exception of ice cores, chronologies However, on Somerset Island, an initial pioneer or cold are frequently insecure. The samples in this site were phase was not recorded. Future work can determine if large and all were based on moss layers in the sediment. this difference is due to some local factor or climate Thus, the chronology is probably more secure than differences between the sites. that of sites RS36 and RS29 from Somerset Island (Gajewski 1995). However, dates on aquatic fossils can Acknowledgements . – This work was funded by the Natural be signiŽ cantly older than those on terrestrial material Sciences and Engineering Research Council of Canada. We thank taken from the same stratigraphic level (MacDonald et the Polar Continental Shelf Project for logistic support. This paper al. 1991) and the chronology of this site may suffer from is PCSP Contribution No. 02000. We thank C. Rintz and N. Thi- beault for performing the X-rays, L. Ley for identifying the mosses this problem. and M. Sawada for assistance in producing the location map. We The sediment from the base to around 90 cm was also thank the Metallurgical Technology Centre, Mineral Science apparently deposited in 2500 years; the time between Department at Falconbridge Ltd., for use of the laser particle size the presumed emergence from the sea (Dyke et al. analyser. 1992) and the lowest radiocarbon date in the core. 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