Variations in Elastic Thickness in the Canadian Shield

We have used different spectral methods (Blackman-Tukey, Multitaper, and Maximum Entropy) to determine from the coherence between Bouguer gravity and topography the variations of the effective elastic thickness (T_e) of the lithosphere in the Canadian Shield. These methods differ mostly by their spatial resolution (1,000 to 2,000km) determined by the width of the windows applied to the data sets to obtain the spectral estimates but yield comparable results and the maps of T_e show similar trends. The highest resolution is obtained from the maximum entropy method. The Canadian Shield includes several geological provinces ranging in age from Archean to mid Proterozoic. The effective elastic thickness varies from <30km to >100km over distances comparable to the width of the moving window. There is no clear relationship between elastic thickness and age as high and low values of T_e are found within each of the geological provinces. The map of T_e does not show a clear geographic pattern with high elastic thickness values found near the edge as well as near the center of the continent.