Siliceous microfossils in a Holocene, High Arctic peat deposit (Nordvestø, northwestern Greenland)

Abstract

Siliceous microfossils (diatom valves, chrysophyte stomatocysts, and testate amoebae plates) were examined from a 2.6-m thick peat deposit from Nordvestø, northwestern Greenland (76°44′N, 73° 13′W). The moss, predominantly Aplodon wormskioldii (Hornem.) R.Br., began to accumulate approximately 6500 years ago and persisted for about 2000 years. Siliceous microfossils were generally well preserved in the peat, although taxon richness was low (i.e., only 19 diatom taxa, 16 chrysophyte cyst morphotypes, and 4 testate amoebae genera). Despite the paucity of taxa, marked shifts in species composition were recorded. Geochemical analyses and biogenic silica determination on the peat did not show any significant trends. To our knowledge, this study represents the first such combined analysis of a High Arctic peat, so our interpretations should be considered tentative. Environmental variables were not stable during the 2000 years of peat accumulation, as suggested by microfossil assemblage changes. For example, about 5000 years BP, diatoms reached their maximum relative abundance with taxa indicative of wetter habitats. We hypothesize that an influx of meltwater to the peat may have occurred at this time, perhaps because of wetter conditions or larger accumulations of snow during winter. These preliminary data indicate that siliceous microfossil analyses from arctic peat cores may eventually fine-tune paleoecological inferences for this climatically important region, once the environmental variables determining species distributions in peat deposits are determined. Key words: peat deposits, Greenland, diatoms, chrysophyte cysts, protozoan plates, paleoecology.