Exhuming the Canadian Shield: preliminary interpretations from low-temperature thermochronology and significance for the sedimentary succession of the Hudson Bay Basin

The geological history of the Canadian Shield is difficult to constrain because the sedimentary record is missing in those areas where Precambrian basement is exposed at the surface. This study presents preliminary results and interpretations of new apatite fission-track (AFT) analyses to elucidate the low-temperature (< 120 °C) history across Canada. The AFT modelling of samples from Southampton Island, in Nunavut, indicates that maximum temperatures varied between 62 and 93 °C during the Phanerozoic. Maximum burial occurred in the Devonian, but a second phase of Mesozoic burial is proposed, especially in the case for the sample recovered closest to the northern island-bounding normal faults. The AFT modelling of a sample from northern Ontario indicates a maximum burial temperature of approximately 75 °C was reached during the Late Devonian. Overall, these results demonstrate that the Hudson Bay sedimentary succession is the remnant of a more extensive and thicker sedimentary cover than is preserved. This study also provides the opportunity to discuss innovative methodology and modelling approaches for low-temperature thermochronology.