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TitleChlorine-36 age determination for Mystery Creek rock avalanche, British Columbia, Canada
AuthorBlais-Stevens, A; Hermanns, R L; Jermyn, C
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2011 p. 1; 1 CD-ROM
Year2011
Alt SeriesEarth Sciences Sector, Contribution Series 20100388
MeetingGeological Association of Canada Annual Meeting; Ottawa; CA; May 25-27, 2011
Documentserial
Lang.English
Mediapaper; CD-ROM; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92G/06; 92G/11; 92G/14; 92J/02; 92J/07
AreaSea to Sky Corridor; North Vancouver; Lions Bay; Porteau; Squamish; Whistler; Pemberton
Lat/Long WENS-123.5000 -122.5000 50.5000 49.2500
Subjectsengineering geology; geochronology; health hazards; landslides; landslide deposits; slope stability; slope failures; chlorine; radiometric dating
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
LinksOnline - En ligne
AbstractThe 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.
GEOSCAN ID287796