Role of thermal refraction in localizing intraplate deformation in southeastern Ukraine

Abstract

The relative importance of the various factors that lead to intraplate deformation has been difficult to establish. Modelling results show that compressional deformation of a thick sedimentary basin in southeastern Ukraine was facilitated by strain localization resulting from the contrast in thermal conductivity between the basin and the surrounding crystalline crust. Although tectonic plates are deformed mostly at their boundaries, plate interiors can also show considerable non-rigid behaviour1,2,3. The deformational response of plate interiors to tectonic forces depends on composition and texture, temperature and confining pressure, strain rate, presence of fluids and pre-existing structure. However, the relative importance of these factors has been difficult to establish4. Here we use numerical modelling constrained by geological and geophysical data to assess the factors controlling intraplate deformation in southeastern Ukraine. The model’s starting point was the steady-state thermal structure in an otherwise tectonically stable but heterogeneous lithosphere. Our results show that compressional deformation and uplift of the thick Dniepr–Donets sedimentary basin was facilitated by strain localization resulting from temperature effects (thermal refraction) produced by the contrast in thermal conductivity between the sedimentary fill of the basin and the surrounding crystalline crust. We suggest that in settings where thick sedimentary basins occur in cold lithosphere, intraplate deformation can occur simply because of thermal conductivity contrasts, and the reactivation of inherited mechanical weaknesses may not be necessary.