1 Department of Geoscience, Science and Technology, Aarhus University2 Department of Earth Sciences, Faculty of Science, Aarhus University, Aarhus University3 Department of Geoscience, Science and Technology, Aarhus University
A number of sources contribute to the lithospheric stress field. Lithospheric density heterogeneities cause horizontal gradients of the vertically integrated lithostatic pressure, which give rise to gravitational/geopotential stresses. Variations of pressure, temperature and composition in the convecting mantle cause mantle tractions at the base of the lithosphere. The radial component can cause dynamic topography and an anomalous state of lithospheric pressure, whereas the horizontal component might influence the plate movements directly. Relative plate movements and stress transmission through the rigid plates result in forces along plate boundaries. The relative importance and absolute magnitudes of the single stress sources is still matter of considerable discussion. Whereas the crustal structure is relatively well constrained for the estimation of the geopotential stress component, the thickness and density structure of the mantle lithosphere is more uncertain. The compositional and thermal state of the lower mantle, linked to mantle convection and pressure inhomogeneities are still generally unknown. We developed a method to model and analyse geopotential stresses, including the pressure and temperature variations at the base of the lithosphere that result in dynamic topography, and an anomalous geopotential energy. We do not include horizontal basal tractions or plate boundary forces. Nevertheless we can indirectly discuss the importance of additional stress sources for the lithospheric state of stress. The North Atlantic Realm and surrounding continental areas are well suited for the presented modelling approach. The area is dominated by spreading ridges and the Iceland melt anomaly, while stress effects from continental collision and subduction are relatively remote. Using a global finite element approach, we analyse the potential energy related stresses in the North Atlantic Realm. The most important contributions to stresses are variations of lithospheric, basal pressure and topography. The modelled principal stress directions compare well with the World Stress Map. We furthermore discuss the geodynamic implications for the region, such as the influence of the Iceland melt anomaly, the stress state of passive margins and stress patterns inherited from the opening of the North Atlantic.
Plate Tectonics; North Atlantic; Stress; Lithosphere