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Abstract:
Glacial isostatic adjustment (GIA) leads to remarkable stress changes in the subsurface which can be potentially released along favourably orientated pre-existing fault structures, a process nowadays termed glacially triggered faulting. A notable vertical shift of some meters can occur. In coastal areas this can affect the measured elevation of relative sea level markers. In such case these markers must be corrected before they can be used in palaeo-sea level investigations.
Compared to Fennoscandia, the vast area of Canada does, so far, not contain any prominent traces of glacially triggered faulting which has led to interesting speculations in the literature. We will briefly review any suggested glacially induced faults in Canada and then analyze GIA-induced stress changes from a 3D finite element model of North America. We thereby test different stress regimes and (hypothetical) fault configurations to identify the most plausible fault parameters for reactivation. We will highlight the best parameter combinations for each fault or location of concern and compare them to available field observations. We will show that glacially triggered faulting has very likely affected most parts of Canada, including intraplate areas and Arctic islands. One example suggests that some relative sea level markers should be carefully used because faulting may have shifted the sample to a new elevation.
