Evidence for evaporite diapirism in northeastern Mexico

Several authors have reported intrusive gypsum in northeastern Mexico. Salt diapirism also has been inferred. Recent evidence from cores indicates that the complete sequence of evaporites behaved as a mobile unit in response to tight folding. The "Minas Viejas" salt (Jurassic) has a steeply dipping planar fabric in both Sierra del Fraile, where gypsum diapirism already has been documented, and in Sierra de Minas Viejas. The salt in Sierra de Minas Viejas is abnormally thick. It seems reasonable to conclude on this basis that Minas Viejas is also a true diapir. Because of the large scale of the mobility, however, it is of no great consequence whether or not actual piercement has occurred.