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 ($T_e$) 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 $T_e$ projected onto a grid by inverting the cross-spectral properties (admittance and coherence) between Bouguer gravity and topography data obtained from a continuous wavelet transform. Continental $T_e$ 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 $T_e$ and lithospheric thickness obtained from calibrated upper mantle surface wave tomography models. Further comparing the $T_e$ distribution with orogenic age data shows that 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 $T_e$ 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 $T_e$ and the thermal, compositional and rheological structure.
Dr. Zhezhe Lu
Postodoctoral Researcher
My research interests include Geophysics, Tectonophysics, Lithospheric Attributes, Gravity Inversion.