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TitlePrehistoric sensitive clay landslides and paleoseismicity in the Ottawa Valley, Canada
AuthorBrooks, G R
SourceLandslides in sensitive clays; by L'Heureux, J -S (ed.); Locat, A (ed.); Leroueil, S (ed.); Demers, D (ed.); Locat, J (ed.) ; AIGAS / IWLSC; Advances in Natural and Technological Hazards Research vol. 36, 2014 p. 119-131, 10
Alt SeriesEarth Sciences Sector, Contribution Series 20120421
PublisherSpringer Netherlands
Mediaon-line; digital; paper
RelatedThis publication is related to Brooks, G R; Brooks, G R; (2013). Prehistoric sensitive clay landslides and paleoseismicity in the Ottawa Valley, Canada; Prehistoric sensitive clay landslides and paleoseismicity in the Ottawa Valley, Canada, 1st International Workshop on Landslides in Sensitive Clays, Program and abstracts booklet
File formatpdf
ProvinceOntario; Quebec
AreaOttawa River valley
Lat/Long WENS -76.0000 -74.0000 46.0000 45.0000
Subjectssedimentology; geochronology; landslide deposits; landslides; erosion; mass wasting; radiocarbon dates; sensitive clays; clays; Quaternary
Illustrationslocation maps; tables; histograms; plots
ProgramEastern Canada Geohazards Assessment Project, Public Safety Geoscience
AbstractThe ages of 39 large retrogressive landslides and three areas of disturbed terrain in the Ottawa Valley were compiled using 122 published and unpublished radiocarbon ages. The chronological dataset includes 15 confined-valley landslides, 23 scarp-side landslides, and four special case features (one massive landslide, three disturbed terrain areas). The ages of the features range from 'modern' to 8,000 14C cal BP. Distinct clusters of 10 and 11 coincidentally-aged landslides at ~1,000 and ~5,150 14C cal BP are the groups of landslides previously interpreted to have been triggered by paleoearthquakes. Scarp-side landslides with scars between 0.1 and 10 km2 are the dominant failure morphology forming the two age clusters and constitute an important component of the interpreted paleoseismic evidence. Five of the confined-valley landslides are part of the ~1,000 14C cal BP cluster, but the other ten failures are of widely varying ages. One of the special case features, a massive landslide originating from a source area of ~20 km2, falls within the ~1,000 14C cal BP cluster. Radiocarbon ages representing the age of the Treadwell and Wendover disturbed terrains, suggest that these areas are contemporary with the Lefaivre disturbed area at ~7,900 14C cal BP, but this is not an unequivocal interpretation. Notwithstanding sampling bias within the dataset, it is inferred from the high proportion of dated landslides falling within the two interpreted paleoearthquake clusters that there is a ‘strong’ paleoseismic signature within the temporal pattern of landsliding within the Ottawa Valley. Based on the Ottawa Valley dataset, scarp-side landslides with preserved debris fields and scars greater than 0.1 km2, and landslides in general with scars greater than 1 km2, are more promising targets than confined-valley landslides for paleoseismic studies.
Summary(Plain Language Summary, not published)
There are hundreds of sensitive clay landslides in the Ottawa Valley, Ont.-Que., most of unknown prehistoric age. This study has compiled ages for 38 landslides and 3 'landslide-like features; the ages span 8000 years. The ages of 20 landslides are similar and form two distinct age clusters at about 1000 and 5150 years ago. These clusters have been interpreted previously to be evidence of ancient earthquakes in the area. This paper makes generalizations on the scale and morphology of the landslides within these two clusters to aid future studies looking for evidence of past earthquakes. It also makes the deduction that a future significant earthquake in the area may triggered multiple sensitive clay landslides, as has occurred in the past.