Pressure-driven upper-mantle flow in the Indo-Atlantic Realm since the Upper Jurassic inferred from continent-scale hiatus surfaces and oceanic spreading rate variations

Mantle convection is a fundamental process responsible for shaping the tectonic evolution of the Earth. It is commonly perceived that mantle convection is difficult to constrain directly. However, it affects the horizontal and vertical motion of the lithosphere. The former is observed in the spreading rates, while the latter leaves various imprints in the geological record. In particular, the positive surface deflections driven by mantle convection create erosional/non-depositional environments, which induce gaps (hiatus) in the stratigraphic record (i.e., an absence or thinning of a sedimentary layer). Modern digital geological maps allow us to map long-wavelength no-/hiatus surfaces at continental scale systematically.

Here we compare our continent-scale hiatus mapping to plate motion variations in the Atlantic and Indo-Australian realms from the Upper Jurassic onward. In general, we find the datasets correlate except when plate boundary forces may play a significant role. There is a timescale on the order of a geologic series, ten to a few tens of millions of years (Myrs), between the occurrence of continent-scale hiatus and plate motion changes. This is consistent with the presence of a weak upper mantle. Furthermore, we find significant differences in the spatial extent of hiatus patterns across and between continents, which means they cannot simply be explained by eustatic variations but should be linked to variations in the upper-mantle flow.

Our results highlight the importance of geological datasets to map the temporal evolution of geodynamic processes in the deep Earth. Also, they imply that different timescales for convection and topography in convective support must be an integral component of time-dependent geodynamic Earth models. Studies of horizontal and vertical motion of the lithosphere to track past mantle flow would provide powerful constraints for adjoint-based geodynamic inverse models of past mantle convection.