Paleostress characterization of the “Wallachian phase” in its type area (southeastern Carpathians, Romania)

The “Wallachian phase” is defined in the East Carpathians, a convex to the east mountain belt in Romania, as a tectonic event occurring between Pliocene and Quaternary times. This event formed folds and minor thrusts, structures that are usually located in internal parts of the somewhat older fold-and-thrust belt structure. This location contrasts with the location one would predict from their recent age, and contrasts with the older, Cretaceous-middle Tortonian, piggyback thrust mode of propagation. In the southeastern Carpathians, this late overstep sequence of thrusting resulted from a modification in the stress field. Our data indicate that the direction of compression changed from NW–SE to N–S during middle-Tortonian time. This is further supported by stratigraphic dating of structures, and thereby paleostresses, indicating that the Wallachian episode was not a brief event at the Pliocene-Quaternary boundary, but lasted from middle Tortonian to early Pleistocene.