Effective elastic thickness T_e of the lithosphere in western Canada

Abstract

[1] A stochastic relationship between topography and Bouguer gravity is used to calculate high-resolution variations in effective elastic thickness, T e , of the lithosphere in western Canada. The topography-gravity coherence is calculated using a two-dimensional, maximum-entropy-based spectral estimator. This method allows for smaller data windows and provides T e determinations with higher spatial resolution than standard Fourier spectral estimators. Our analysis shows significant variations in T e in western Canada. T e increases from $20-40 km in the weak, young portions of the Cordillera to 100 km and greater in the strong, old Canadian Shield. T e estimates are in good agreement with lithospheric temperatures calculated from surface heat flow and radioactive heat generation data. Our calculated T e distribution also shows strong correlation with other thermally related geophysical parameters, such as lithospheric age, regional heat flow, seismicity, seismic properties, and the stress field. Consequently, we infer that lithospheric temperatures exert a primary control on large-scale variations in T e . Collectively, the correlations readily explain why the Craton continues to be stable and undeformed, whereas the Cordillera has continued to be deformed through the Cenozoic. An exception is the Wopmay Orogen, which includes the easternmost part of the northern Cordillera. There T e is $90 km, although the surface heat flow is $90 mW/m 2 . We infer that the high heat flow in this region is caused primarily by very high radioactive heat generation in the upper crust and that deep lithospheric temperatures are moderately low as expected from its age and long-term geological stability.

Linear or nonlinear rheology in the mantle: a 3D finite-element approach to postglacial rebound modeling

“…The model has a 120 km elastic lithosphere and a 2770 km mantle, whose density and elastic properties vary vertically according to PREM (Dziewonski and Anderson, 1981). The lithospheric thickness we adopted is consistent with the estimates given by Flück et al (2003) for the Canadian Shield. The mantle is rheologically uniform, both vertically and laterally, and the deformation is controlled by a mixed flow-law (Gasperini et al, 1992), including the linear Maxwell body relation and the power-law equation shown below:…”

An accuracy assessment of the fan wavelet coherence method for elastic thickness estimation

“…As for the Forsyth approach with a variable z m (x), the wavelet-adapted equations for the Banks method can account for a variable z l (x) if this information is known. Generally speaking, the inclusion of a thin layer between the surface and Moho serves to reduce T e estimates, though not significantly, with 1999] and Flück et al [2003] finding their results to be fairly insensitive to the magnitude of the density contrasts or depth of the interface, albeit using different approaches to that of Banks et al [2001].…”

The electrical resistivity of Canada’s lithosphere and correlation with other parameters: contributions from Lithoprobe and other programmes

“…Thinnest elastic thickness on the North American Craton, <40 km, is found beneath the Williston Basin in southern Saskatchewan correlative (2) Shaocheng, J., Rondenay, S., Mareschal, M., and Seneschal, G., 1996 1985Majorowicz and Gough (1991; Gough and Majorowicz (1992); Majorowicz et al (1993aMajorowicz et al ( , 1993b; Majorowicz and Gough (1994) (2014) with the trace of the Trans-Hudson Orogen. For the Cordillera, elastic thickness is in the range 20-40 km (Fluck et al 2003).…”