Stress field evolution in a plate interior

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Intraplate tectonics, the weak deformation of lithospheric plate interiors, is often a reflection of processes affecting the plate margins and usually documents a sequence of different stress fields over geological time. Plate interiors should be better recorders of regional long-term stress fields than plate margins, because they do not suffer strong deformation, localized vertical-axis rotations or strain partitioning. Also, local stresses arising from high topography play no role there. On the other hand, their stratigraphic sequences are frequently incomplete, typically reflecting slow subsidence punctuated by low-magnitude uplift. Angular unconformities or syn-kinematic strata are often not available to constrain the timing of deformation events. Even where a relative chronology of events can be established, the age assignments are commonly based on circumstantial evidence and potentially circular. Central Europe is an ideal place to study intraplate deformation and its relation to plate boundaries. It is bounded by the Mid-Atlantic ridge on one side and the Mediterranean collision zone on the other. A history of different tectonic regimes and stress fields is clearly established, and it comprises one of the most spectacular examples of intraplate shortening worldwide. Even so, there is no consensus on the kinematic sequence, the precise timing and areal extent of the different tectonic regimes, or the plate margin events they reflect. We propose to study the Meso-Cenozoic tectonic evolution of Central Europe in a contiguous region of 300 x 150 km size, aiming at the best spatial coverage obtainable. Detailed slip analysis of fracture populations will be combined with analysis of the map-scale structures in which they occur. This will allow us to identify pre- to post-tilt relative chronologies, and to estimate the strain magnitudes associated with the individual stress states. In order to produce independent, non-circular age estimates, we will combine fault-slip analyses of crystalline rocks with K-Ar dating of fault gouge. The viability of U-Pb dating of calcite from slickenfibers and veins will be tested through LA-ICPMS geochemical analyses of U and Pb contents. Dating will be attempted if suitable, clean calcites of sufficiently high U content are encountered. The intraplate tectonic history derived will be used to re-evaluate its links with opening of the North Atlantic and the evolution of the Mediterranean, including earlier studies.