Modelling rates and distribution of subsidence due to dynamic topography over subducting slabs: is it possible to identify dynamic topography from ancient strata?

Dynamic topography formed over subducting oceanic lithosphere has been prop osed as a mechanism to explain certain otherwise anomalous long-wavelength patterns of subsidence inferred from ancient strata. Forward modelling of m antle flow in response to a subducting slab predicts amplitudes and distrib utions of dynamic topography that may occur due to various subducting slab geometries and histories. Plotting calculated dynamic topographies at a poi nt against time produces tectonic subsidence curves. These subsidence curve s show features such as evolution from convex to concave shape, amplitudes up to similar to 2000 m, subsidence rates up to similar to 220 m Myr(-1), a nd a general decrease in subsidence amplitude away from the subduction zone , over a distance of similar to 2000 km. On many convergent continental mar gins, dynamic topography is likely to be superimposed on other subsidence m echanisms. In back-arc basins, subsidence due to dynamic topography should be distinguishable from that due to extensional tectonics based simply on t he temporal subsidence evolution expressed in the subsidence curve shapes. In a foreland basin setting, comparing dynamic topography models with forwa rd models of flexural loading suggest the two processes can generate simila r temporal subsidence patterns, but that dynamic topography causes subsiden ce over significantly greater wavelengths. Matches between calculated subsi dence due to dynamic topography and backstripped subsidence patterns from U pper Cretaceous strata of the Western Interior Basin, USA, support the hypo thesis that a long-wavelength 'background subsidence' was caused by dynamic topography.