A Field Guide to the Spectacular Salt Mines of the Transylvanian Basin and Romanian Carpathians

Salt diapirs/bodies are remarkable structures often presenting a rich internal structure, with features like isoclinal folds, sheath folds, curtain folds, boudinage, etc. Salt structures are themselves valuable as a resource but are also often associated with significant hydrocarbon accumulations, as well as valuable as storage sites. While significant progress has been made to imagine the external geometry of salt bodies, especially using 3D seismic, the complex internal structure of the salt diapirs is less known. Such structures can mainly be investigated using salt mines, outcrops, physical models and rarely seismic for larger structures. There are just a few places in the world where salt mines or outcrops can be studied, and Romania is such an example. The Romanian Carpathians and the Transylvanian Basin offer access to multiple salt mines (and outcrops) which are easily accessible especially because most of the salt mines have been converted into public treatment facilities. The walls of the galleries have been cleaned, polished and well lighted, offering unique 3D exposures which can be used to observe and map in detail the deformation of these salt domes. In this field-trip guide, we propose a route with five stops, visiting four salt mines and one important location from the link between salt tectonics and hydrocarbons. Each of the chosen locations is unique as it records a different regional kinematic evolution and offers the opportunity to compare and contrast the specific internal structures.