Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ 1 roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena.
a IRSN, BP 17, 92262 Fontenay-aux-Roses cedex, France
b UMR CNRS 7566 G2R, université Henri-Poincaré, Nancy-1, BP 239, 54506 Vandoeuvre-lès-Nancy, France