Joint analyses of calcite twins and fault slips as a key for deciphering polyphase tectonics: Burgundy as a case study

Abstract

Determination of regional paleostresses based on calcite twin analysis has been successfully applied for the first time in the Burgundy platform, France. Paleostress tensors obtained with this method are internally consistent along the profile studied. Moreover, the same directions of paleostresses are independently inferred from fault striation analysis. The results clearly show that the late Mesozoic-Cenozoic evolution of the area has involved polyphase deformation, including 1. (1) NNE-SSW extension, probably late Mesozoic in age, 2. (2) N-S compression related to a major orogenic event in the Pyrenees and Provence, late Eocene in age, 3. (3) E-W extension related to the Oligocene rifting event (the Rhine-Saône rift system), 4. (4) WNW-ESE compression related to the Late Miocene westward thrusting of Jura. Calcite twin and striated fault analyses are two complementary tools for paleostress determination: their combined application will allow accurate mapping of paleostress trajectories in intraplate tectonics setting. Moreover, calcite twins can allow stress and paleostress determination when macroscopic features are not observable, which is often the case in very weakly deformed areas and in drill holes.