Abstract

Earth's tectonic history is punctuated by several cycles of supercontinent assembly and breakup that profoundly influenced the lithospheric structure; however, the roles of the various factors controlling continental strength and deformation during the cycles remain debated. The effective elastic thickness (Te) reflects the lithosphere's long-term, depth-integrated strength and is useful for deciphering the complex evolution of continents. In this study, we estimate a new global map of continental Te projected onto a 15′×15′ grid by inverting the cross-spectral properties (admittance and coherence) between Bouguer gravity and topography data obtained from a continuous wavelet transform. Continental Te ranges from <5 to ∼140 km, with a mean and standard deviation of 50 and 33 km, respectively. Based on a gaussian mixture model-based cluster analysis, we delineate tectonically active provinces, stable Archean cratons and transitional lithosphere. We find an obvious positive correlation between Te and lithospheric thickness obtained from calibrated upper mantle surface wave tomography models. Further comparing the Te distribution with orogenic age data shows that Te exhibits a clear time dependence where the strength is governed by the time since the last orogeny. Based on plate cooling models, we indicate that continental Te corresponds approximately to the depth of the 300±150∘C isotherm. These results favour a diffusive (cooling) model that considerably influences the strength of the continental lithosphere, despite the complex relation between Te and the thermal, compositional and rheological structure.