Investigating Precambrian Tectonics in Northernmost Hudson Bay: Insights from Joint Inversion of Receiver Functions and Surface Waves

English Abstract:

How tectonic processes operated and changed through the Precambrian still remains a matter of debate: when did plate tectonics as we observe on Earth today begin, and did different processes occur on the younger, hotter Earth? The Canadian Shield contains one of the largest exposures of Precambrian rocks on Earth, and the rocks of the northernmost Hudson Bay region span more than 2 billion years of Earth’s history, from 3.9-1.8 Ga. This is thus an important locality for trying to understand the processes that may have occurred on the early Earth.

Previous geophysical work in northernmost Hudson Bay has shown interesting variations in crustal properties within this region. These variations appear to relate to differences in tectonic processes operating when distinct parts of the crust in northernmost Hudson Bay formed. In this study we use data from broadband seismic stations in northernmost Hudson Bay including from the POLARIS network to obtain new shear velocity models for the crust and upper mantle in northernmost Hudson Bay by jointly inverting P receiver functions and ambient noise surface wave dispersion measurements. A joint inversion for shear velocity reduces the inherent ambiguities in each individual method, while constructing a model that is consistent with both. These models are used to estimate crustal thicknesses within this region. Variations in crustal thickness and shear velocity are interpreted with respect to changes in tectonic processes over time.