The evolution of calcite microstructures and crystallographic preferred orientations (CPOs) is well understood due to well constrained experimental studies. However, the interpretation of naturally deformed calcite marbles is more difficult because of less constrained strain paths, a multiphase deformation history, and variable P–T conditions. The Penninic units within the Tauern Window (Eastern Alps) have been affected by several deformation events and metamorphic overprint. Generally, three major deformational events can be distinguished. D1 is related to underthrusting of Penninic units beneath the Austroalpine nappe complex, and top-to-the-N nappe stacking within the Penninic continental units. Deformation stage D2 is interpreted as reflecting the subsequent continent collision between the Penninic continental units and the European foreland. D3 is related to the formation of the dome structure of the Tauern Window. This polyphase deformation history can be partly reconstructed by the evolution of calcite microfabrics and CPOs.

Basic concepts of microtectonics are introduced and discussed in this chapter. The study of thin sections of rocks, which was originally mainly petrographic, has evolved during the last century to include a number of structural characteristics, that constitute the microstructure or fabric of a rock. The study of this fabric can be used to reconstruct the structural and metamorphic history, but also to improve the understanding of deformation and metamorphic processes.