Multi-proxy Holocene palaeoclimatic record from a saline lake in the Canadian Subarctic

• Published in: The Holocene
• Main Authors: Pienitz, Reinhard, Smol, John P., Last, William M., Leavitt, Peter R., Cumming, Brian F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 2000
• Subjects: Subarctic; Yukon
• Online Access: http://dx.doi.org/10.1191/09596830094935; http://journals.sagepub.com/doi/pdf/10.1191/09596830094935

Multi-proxy palaeolimnological analyses of a postglacial sedimentary sequence at a centennial-scale resolution from an athalassic saline lake in the Yukon were conducted to infer patterns of Holocene climatic change in the Canadian Subarctic, using sediment mineralogy and biostratigraphy (diatoms, pigments). Diatominferred quantitative estimates of palaeosalinity were obtained by use of transfer functions developed from a calibration set of 219 lakes from western North America. The sediment mineralogy and fossil pigments at the base of the core indicated a moderately deep non-stratified lake dominated by clastic influx, probably in a basin fed by glacial meltwater. The early-Holocene history ( c. 11 000–8100 14 C yr BP) was characterized by a relatively deep mesosaline lake with diatom-inferred salinities approximating 20 g L -1 . The occurrence of both aragonite and dolomite, as well as elevated concentrations of chlorophyll and carotenoid pigments, support the interpretation of deepwater anoxia and possibly strong chemical stratification. High concentrations of the chemically stable b-carotene suggest that total algal abundance was particularly high during the early Holocene, when planktonic Cyclotella cf. choctawhatcheeana and Chaetoceros muelleri were the most common diatom taxa. Relatively fresh (2–15 g L -1 ) eutrophic conditions prevailed during the mid-Holocene period ( c. 8000– 2000 yr BP), with four periods of alternating fresh and saline conditions. The diatom-inferred salinity profile reveals significant fluctuations within these cycles, but overall they indicate humid climatic conditions compared to today. Algal abundance is inferred to have declined three-fold relative to the early Holocene, particularly in the case of eukaryotic algae (e.g., diatoms, cryptophytes, chlorophytes). The recent history of the lake (about 2000 years BP until the present day) was marked by important changes in ionic composition (e.g., occurrence of gypsum and Mg-carbonates) and hydrologic conditions. The lakewater ...