Dynamic Topography and Intraplate Basins – an Explanation for Anomalous Subsidence?

C. Heine and R. D. Müller. EarthByte Group, School of Geosciences, The University of Sydney, Camp Baxter - H11 Demountable Village, Codrington Ave, The University of Sydney, NSW 2006, Australia, phone: +61 2 9351 4257, fax: +61 2 9351 0184, christian@geosci.usyd.edu.au

Wide intraplate basins often show a component of anomalous tectonic subsidence which cannot be explained using conventional rift basin models. It has been proposed that a special type of basement (”accretionary crust”) underlying those basins is more susceptible to changes in the plate-tectonic configuration / far-field stresses and this is reflected by anomalous subsidence behaviour. However, the link between the basement heterogeneity and subsidence remains enigmatic. In order to investigate the driving force behind this anomalous subsidence we have analysed crustal structure data for a global set of more than 250 intraplate basins to compute anomalous tectonic subsidence and differential stretching factor grids. By using the EarthByte/Torsvik plate rotation model and a global mantle convection framework, we extracted the dynamic topography through time from the Mid-Jurassic to present to investigate the long-term influence of mantle convection on intraplate basin evolution. Our study shows that many typical “sag basins” moved from a geoid high, centered on Gondwana, towards relative geoid lows due to the dispersal of Gondwana. This resulted in increasing negative dynamic topography of those basins and thus the creation of “anomalous” accomodation space which cannot be accounted for using conventional basin modelling techniques. It appears that dynamic topography may explain the observed anomalous tectonic subsidence and basin inversion in those long-term depositional regions and it needs to be considered for regional basin modelling studies.

Basin Modeling Advances
2006 AAPG International Conference and Exhibition, (November 5-8, 2006) Technical Program