A long-term context for the 1663 Charlevoix CE earthquake interpreted from the postglacial landslide record in the Gouffre Valley, Quebec, Canada

Abstract

This paper examines the distribution, stratigraphy and chronology of landslide deposits within the Gouffre Valley to provide a long-term context for the 1663 CE M 7.0–7.5 Charlevoix earthquake, Charlevoix-Kamouraska Seismic Zone (CKSZ), southern Quebec, Canada. Our mapping utilized a 1 × 1 m digital terrain model, and we interpreted deposit age and stratigraphy from 30 new AMS radiocarbon ages, supplemented by 51 regular radiocarbon ages and 23 dendrochronology ages compiled from previous studies. These data provide a robust chronological connection between the 1663 CE earthquake and large-scale landslide deposits that cover about 24 km2, extend about 20 km along the valley bottom, and originated from separate source areas. Eight, relatively small-scale (less than 0.48 km2), prehistoric landslide features are also present in the Gouffre Valley, including three dated landslides, aged between about 7950–7300, 6595–6087, and 1310–1200 cal BCE, a poorly-constrained deposit aged between 4782–4452 BCE and 1663 CE, and four landslides of unknown age. There is no evidence to support an earthquake trigger for any of these prehistoric landslides. Instead, the widespread deposits associated with the 1663 CE earthquake represent the only multi-event, landslide signature in the Gouffre Valley. This, in combination with a long gap between early postglacial and late Holocene mass movement activity in several nearby lakes, is consistent with the 1663 CE earthquake being the largest to occur in the CKSZ over the past about 10 ka.