3D multiscale structural analysis of the eastern Paris basin : the Andra* contribution

New structural data, collected in the framework of the Meuse/Haute-Marne Andra site studies, are presented. The approach is typically multiscale from geological mapping and 2D/3D seismic studies, to core analysis, and including paleo-stress reconstruction. Three types of regional structures have been defined from structural field analysis and 2D seismic analysis: (1) NE-SW cover faults disconnected from any basement faults (Gondrecourt and Joinville troughs), (2) NW-SE and NE-SW cover faults directly rooted in the basement (Marne and Roches-Bettaincourt troughs), and (3) NW-SE cover structures de-coupled from basement structures (Poissons and Brouthieres-Soulaincourt fault systems, Savonnieres syncline). The 3D seismic survey shows, in the Dogger, N120° trending structures that could be interpreted as reef constructions similar to those observed in the outcropping Bajocian layers farther to the east. The minor fractures measured in the field as well as in the cores and shafts, and the hydrofracturing tests allowed us to reconstruct the successive stress fields from Jurassic to Present. We emphasise the role of the Eocene and mostly Oligocene tectonic events, which are responsible for not only the main movements along the regional faults but also for the majority of minor structures observed at outcrop scale. The whole combination of the different scales structural analyses allows proposing a comprehensive geodynamic scenario for the studied area.