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TitreNew occurrences of theWhite River Ash (east lobe) in Subarctic Canada and utility for estimating freshwater reservoir effect in lake sediment archives
AuteurPatterson, R T; Crann, C; Cutts, J A; Courtney Mustaphi, C J; Nasser, N A; Macumber, A L; Galloway, J M; Swindles, G T; Falck, H
SourcePalaeogeography, Palaeoclimatology, Palaeoecology vol. 477, 2017 p. 1-9, https://doi.org/10.1016/j.palaeo.2017.03.031
Année2017
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160123
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.palaeo.2017.03.031
Mediapapier; en ligne; numérique
Formatspdf
ProvinceTerritoires du Nord-Ouest; Yukon
Lat/Long OENS-142.0000 -112.0000 63.0000 60.0000
Sujetsdatation au radiocarbone; cendre volcanique; analyses de cendres; lacs; sediments lacustres; chronostratigraphie; sedimentation
Illustrationslocation maps; tables; photographs; graphs
ProgrammeOutils d'adaptation et d'impacts sur l'environnement pour les mines de métaux, Géosciences de l'environnement
Résumé(disponible en anglais seulement)
The freshwater reservoir effect (FRE) in the Canadian Subarctic complicates development of high-resolution age-depth models based on
radiocarbon dates from lake sediments. Volcanic ashfall layers (tephras) provide an absolute chronostratigraphic marker that can be used to estimate age offsets. We describe the first recorded occurrence of a visible lacustrine tephra in the central Northwest Territories (CNT). The tephra, observed in Pocket Lake, near Yellowknife, is geochemically and stratigraphically attributed to the White River Ash Eastern Lobe (WRAe; A.D 833-850; 1117-1100 cal BP), which originated from an eruption of Mount Churchill, Alaska. We also observed the WRAe as a cryptotephra in Bridge Lake, 130 km to the NE, suggesting that records of this tephra are widespread in CNT lakes. The identification of this tephra presents opportunities for use of the WRAe as a dating tool in the region and to quantify the magnitude of the FRE in order to correct radiocarbon age depth models. Two well-dated sediment cores from Pocket Lake, containing a visible WRAe record, indicate a FRE of 200 years, which matches closely with the estimated FRE of 245 years at the lake sediment-water interface. Although additional results from other lakes in the region are required, this preliminary finding implies that FRE estimates for the late Holocene in the region, may be based either on down-core WRAe / radiocarbon age model offsets, or on radiocarbon dates obtained from the sediment-water interface.
Résumé(Résumé en langage clair et simple, non publié)
L'occurrence des cendres de la Rivière Blanche dans les sédiments de lac dans la région centrale des Territoires du Nord-Ouest est documentée. Le décalage de l'âge induit par l'effet de réservoir de l'eau douce pour le carbone est corrigé par téphrochronologie.
GEOSCAN ID299052