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TitreChlorine-36 age determination for Mystery Creek rock avalanche, British Columbia, Canada
AuteurBlais-Stevens, A; Hermanns, R L; Jermyn, C
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 36, 2011 p. 1; 1 CD-ROM
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100388
RéunionGeological Association of Canada Annual Meeting; Ottawa; CA; mai 25-27, 2011
Documentpublication en série
Mediapapier; CD-ROM; en ligne; numérique
SNRC92G/06; 92G/11; 92G/14; 92J/02; 92J/07
Lat/Long OENS-123.5000 -122.5000 50.5000 49.2500
Sujetsdangers pour la santé; glissements de terrain; dépôts de glissement de terrain; stabilité des pentes; glissements de pentes; chlore; datation radiométrique; géologie de l'ingénieur; géochronologie
ProgrammeÉvaluations ciblées des dangers dans l'Ouest du Canada, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The Sea to Sky Corridor has experienced hundreds of historic and prehistoric landslides. The most common types of historical landslides are rock falls and debris flows, which are relatively small in volume, but can be damaging. These types of failures are more common in the southern part of the corridor, between Horseshoe Bay and Porteau, where infrastructure has been built in close proximity to steep slopes. Farther north, fewer landslides have been reported historically, but those that have been recorded, are usually large and date to prehistoric time (e.g., Cheekye fan and Mystery Creek rock avalanche).As part of a Geological Survey of Canada surficial geology and landslide inventory mapping study, Mystery Creek rock avalanche, near Whistler, British Columbia, was sampled for 36Cl dating. Samples were collected from three large flat boulders of quartz diorite in the rock avalanche deposit to confirm a correlation with the previously reported radiocarbon age of 800±100 years BP on charcoal. One sample revealed an age of 2400 years and the other two, 4300 and 4800 years, respectively. These new ages point to four possible interpretations: 1) Mystery Creek landslide is about 800 years old; 2) Based on the overlapping 2 sigma uncertainties, the rock avalanche took place between 2200 and 3600 yrs ago; 3) The rock avalanche deposit is 2400 years old and the other two blocks are too old; and 4) The rock avalanche is between 4300 and 4800 years old. We favour the second where the age range is broader and statistically significant for all three samples. Moreover, at this time, we favour discounting the radiocarbon age based on a greater number of samples analyzed for 36Cl analysis, which indicates an older age with the 2 sigma uncertainty. Thus, large landslides such as these remain a present-day hazard to infrastructure like the Sea to Sky Highway, the railway, and population.