Neotectonics and inferred movements in Canada

Abstract

Neotectonic movements in Canada are due to a variety of causes. Within the Canadian Shield (craton) postglacial rebound appears to be the main contributor. Along the tectonically active western continental margin, plate subduction and transcurrent plate motion are taking place. Further inland there is a region where mantle upwelling is probably the dominant neotectonic process. Along many parts of the passive continental slopes, unconsolidated sediments are being deposited at a rate faster than isostatic adjustments can take place. Postglacial rebound has a strong influence on seismicity in northeastern Canada (Baffin Island-Baffin Bay region). Seismicity along the southeast (St. Lawrence Valley) appears to be due to a reactivation of ancient zones of weakness by the neotectonic stress field; postglacial rebound stress can, at the most, act as a trigger mechanism for seismicity in this region. Long wavelength phenomena that are related to glacial loading-unloading and postglacial rebound can be represented by an elastic-viscoelastic lithosphere and asthenosphere. However, the spatio-temporal behaviour of the pattern of short-wavelength, nonlinear phenomena to postglacial rebound stress and strain depends on the characteristics of these heterogeneities (e.g. faults, blocks and intrusions). Consequently, in structurally heterogeneous regions in Canada and Fennoscandia with similar types of fault patterns and block geometry, a similar spatio-temporal history of postglacial fault offsets and block movements should occur. In other regions where the structural heterogeneities are different, different types and degrees of postglacial movement can be expected.

Keywords

• neotectonics
• uplifts
• glacial geology
• isostacy
• seismicity
• mass movements
• faults
• Holocene
• Canada