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TitleA 7,500 year record of Canadian Subarctic climate dynamics as evidenced by fossil Arcellacea, isotopic signatures and sediment particle size
AuthorMacumber, A L; Patterson, R T; Galloway, J M; Vermaire, J C; Falck, H; Clark, I
Source7th International Symposium on Testae Amoebae abstracts and programme; 2014 p. 28
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20140209
Meeting7th International Symposium on Testae Amoebae; Posnan; PL; September 8-12, 2014
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaCarleton Lake
Lat/Long WENS-107.0000 -106.5000 60.5000 60.0000
Subjectspaleontology; paleoclimates; fossils; fossil distribution; fossil assemblages; carbon isotopes; carbon-14 dates; limnology; Arcellacea; Cenozoic; Quaternary
Programenvironmental impacts and adaptation in the northern environment, Environmental Geoscience
AbstractWe analysed fossil Arcellacea, carbon and nitrogen isotopes, and sediment particle size data from Carleton Lake located approximately 120 km north of the treeline in the central Canadian Subarctic, a vast region sensitive to climate variability but where the Holocene climate dynamics are poorly understood. We observed two significant climate transitions in the proxy records. The first occurred at ca. 5500 cal. yr. BP and is interpreted as being the result of the advance and subsequent retreat of the treeline across Carleton Lake. The treeline migration is evidenced by an upcore increase in percent carbon, an increase in the carbon to nitrogen ratio, and a decrease in the modal grain size. Arcellacean assemblage changes across the transition were characterized by a decrease in the relative abundance of most major taxa with a concurrent increase in the proportion of stressed environment indicator taxa: Centropyxis aculeata ¿aculeata¿ and ¿discoides¿. The second paleolimnological transition occurred at ca. 3500 cal. yr. BP, which corresponds with cooler climatic conditions that prevailed with the onset of the late Holocene Neoglacial. This transition saw the establishment of the modern arcellacean assemblage dominated by Difflugia globula. The interval that followed was characterized by a ¿healthy lake¿ arcellacean assemblage, possibly due to an increase in nutrients washed in from the lake catchment. The cold intervals of the Little Ice Age coincided with decreases in most major taxa and the disappearance from the core record of several species including: Pontiglusia compressa and Difflugia oblonga ¿lanceolata¿. Our results show that over the last century catchment in-wash has declined and that there has been a greater contribution of aquatic plants to the carbon budget. The record from Carleton Lake showcases the sensitivity and value of arcellacean assemblages as paleoclimate indicators.
Summary(Plain Language Summary, not published)
A lake sediment core was obtained from Carleton Lake, located ~120km north of modern treeline in the central Canadian subarctic. We analyzed the subfossil remains of arcellacea, or testate lobose amoebae, carbon and nitrogen isotopes, and sedimentary grain size, to reconstruct the climate history of this site. At ca. 5500 calendar years before present arcellacea assemblages changed, percent carbon and carbon to nitrogen ratios changed, and sedmientary grain size decreased. We interpret these changes to have been in respose to treeline movement across the lake. Another major change in climate change proxies occurred at ca. 3500 calendar years before present, concurrent with the onset of Neoglacial cooling in northern Canada. Cold intervals associated with the more recent "Little Ice Age" also caused shifts in arceallcea assemblages. Our results show that arcellacea can be successfully used to reconstruct paleoclimate in northern areas.