THERMOMECHANICAL STRUCTURE OF EUROPEAN CONTINENTAL LITHOSPHERE - CONSTRAINTS FROM RHEOLOGICAL PROFILES AND EET ESTIMATES

The EET (equivalent elastic thickness) of the lithosphere is a measure of the integrated lithospheric strength. It is directly related to th e mechanical thickness and rheology of the crustal and mantle lithosph ere. We present a comparison of EET estimates and strength profiles ba sed on the extrapolation of rock mechanics data for different parts of the European and Eurasian continental lithosphere. We discuss the tem poral and spatial variations in the mechanical thickness and strength inferred from data for Precambrian segments of Europe's lithosphere, V ariscan Europe and the Alpine collision belt. This analysis demonstrat es important spatial and temporal variations in lithospheric rigidity for orogenic belts and sedimentary basins in eastern and western Europ e and Asian parts of Eurasia. The EET estimates based on synthetic rhe ological profiles constrained by newly available geophysical data are consistent with the estimates of EET derived from flexural studies of sedimentary basins, forelands and orogenic belts. These rheological pr ofiles suggest weakening of the major parts of the European and Eurasi an continental lithosphere by decoupling of the crustal and upper-mant le parts. A comparison with the seismicity-depth distribution for some selected sites suggests that the intra-plate seismicity is essentiall y restricted to the upper crustal parts of Europe's lithosphere, provi ding additional support to the notion of the decoupled lithosphere. Th e presence of intra-plate stress fields can explain a significant part of the observed variations in EET estimates within individual thermot ectonic age groups. A comparison of wavelengths of crustal and lithosp heric folding with observations shows these wavelengths to be consiste nt with estimates of EET inferred from the rheological response of bas ins and orogens at more moderate levels of intra-plate stress.