Synopsis SFB 108 — stress and stress release in the lithosphere

Abstract

‘Stress and Stress Release in the Lithosphere’ has been studied within a Collaborative Research Centre at Karlsruhe University (SFB 108) as special contribution from Germany to the International Lithosphere Program (ILP). This synopsis is an outline of the research results obtained by the SFB 108 as presented in this special volume of Tectonophysics. It starts with a summary of ideas on stress and stress release in the lithosphere which guided the SFB 108 at its beginning in 1981. It is followed by a review of strategy in cooperative research on rift systems, world stress map and the scales of structure of the continental lithosphere from crust to mantle. The main observations are then summarized and connections are made between key results from the various disciplines to obtain new views in lithospheric tectonics. Finally we address open questions and perspectives for future research.The research addressed various styles of continental rifting from the Afro-Arabian rift system to the Central European rift system with the Rhinegraben and the grabens in the French Massif Central as outstanding features. A number of critical parameters such as thickness, heat flow, rheology, composition, strength of the crust and of the lithospheric mantle and the influence of active mantle plumes were identified and classified. Together they strongly influence the style of rifting. Petrophysical modelling of integrated information on seismic velocities, composition and temperature from xenolith analysis, density, gravity and topography provided essential constraints on plume-lithosphere interaction in the French Massif Central and also in the Kenya rift.The Rhinegraben and its Variscan environment offered the opportunity to study different concepts of upper and lower crust, including the occurrence of deep crustal earthquakes and the role of an Alpine detachment.A special concern of the SFB 108 was the distribution of dimensions of heterogeneities in the lithosphere and its relation to the scales of their generating processes. The crust-mantle boundary was recognized as a major change in scales of heterogeneities by deep seismic sounding (DSS) methods applied to the lower crust and the lithospheric mantle. The study of the tectonic stress in western Europe revealed that the crust is in frictional equilibrium down to midcrustal levels and is also decoupled from the mantle allowing adjustive motions of blocks and independent subduction in the foreland of the Alps. This decoupling is achieved in a thin and hot lithosphere driven by mid-Atlantic ridge push and Alpine continent-continent collision. It is described in a quantitative dynamic model of crust-mantle decoupling. The SFB 108 has shown that earth scientists have to rediscover the importance of pattern recognition if complex influences are to be recognized.