Tidal gravity anomalies as a tool to measure rheological properties of the continental lithosphere: application to the South American Plate

Characterization of the bulk physical properties of individual tectonic units is important for understanding the dynamics of continental evolution. One important parameter is effective elastic thickness (Te), a measurement of the flexural strength of the lithosphere. Te is traditionally estimated by examination of the transfer function between gravity and topography. Sparse gravity data coverage limits the application of this method in South America. Instead, we use an empirical correlation (as defined by data from Australia and by the world databank) between tidal gravity anomalies and Te to estimate Te for tectonic units of South America. Our results are consistent with independent determinations of Te in several sub-regions of South America. Although the empirical correlation appears to be quite strong, further research needs to be done to develop a physical theory for the connection between gravity tide anomalies (which sample an essentially instantaneous rheological response of the Earth) and Te (which measures the rheological response of the Earth at geological time scales).