Upper Mantle Controls on the Phanerozoic Evolution of Western and Central Europe

Shear-wave tomography models of the upper mantle below Western and Central Europe are indicative of a thermally very heterogeneous lithosphere-asthenosphere system. High shear-wave velocities indicate a deep 1300 °C isotherm and thus a thick (ca. 200 km) lithosphere in the southwestern North Sea and the Paris Basin. This contrasts with a shallower (< 120 km) lithosphere-asthenosphere boundary across the European Cenozoic Rift System and much of the British Isles. These major, long-wavelength thickness fluctuations of the thermal boundary layer are locally superposed by a number of smaller-scale thermal anomalies reaching into the lithospheric mantle (such as the Eifel mantle thermal anomaly). Previous work indicates that the distribution of earthquakes in this region is related to density and strength variations inside the mantle lithosphere that affect the localization of present-day crustal deformation. With this contribution, we explore and discuss the potential ages of the imaged upper mantle thermal anomalies in an attempt to delineate their roles in the geological past. Thereby we make use of the multiphase tectonic evolution recorded in the overlying sedimentary systems and crystalline crust. To evaluate if and where the upper mantle structure may have controlled Paleozoic to Cenozoic crustal deformation phases, we investigate spatial correlations between upper mantle temperature variations as derived from shear-wave tomography models with major crustal structures of known geological age and tectonic setting. Our new findings provide important observational constraints for geodynamic models of Western and Central Europe – a region affected by glacial isostatic adjustment, foreland orogenic processes as well as extensional and passive margin tectonics.