ABSTRACT: Age of landslides along the Grandes Riviere de la Baleine Esturary, eastern caost of Hudson Bay, Quebec (Canada)

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Abstract

A 12 km long terrace along the estuary of the Grande Riviere de la Baleine, northern Quebec (55 17 N, 77 47 W), has been locally modified by seven large landslides during the last 3,200 14C years. The oldest undated landslide occurred between 3,200 B.P. (formation of the upper terrace) and 2,200 B.P., i.e. the radiocarbon age of the second oldest landslide. The third one occurred around 900 B.P. sometime before peat started to accumulate on the flowbowl floor. The more recent landslides were dendrochronologically dated. They were formed in less than 30 years, i.e. in 1818 (2 synchronous landslides), 1839 and 1846 A.D. These 19th-century landslides were dated through a comparative analysis of growth curves derived from buried trees found in the flowing sediments or from tilted and cut trees, with the regional master chronologies and the northern Quebec light-ring chronology, using more specifically the 1816 and 1817 light-ring years. The 1818landslides occurred during the growing season (July), whereas the 1839 and 1846 landslides were formed during spring. The occurrence of numerous landslides during this short period seems to be related to sustained cool and humid climatic conditions that may have enhanced the subsoil water content.

Bibliography of Canadian Geomorphology