Cavidades en arcilla en el Barranco de Los Sorianos (Bardena Negra).

In the Black Bardena (semi-desert region located in the South of Navarra) are important systems of chasms and caves in clays of Tudela Formation, of Miocene age (Tertiary). The cavities are essentially formed by processes of piping in dispersive clays rich in sodium salts. To a lesser extent dissolution and precipitation of secondary minerals in the form of speleothems occur. Examples found in recent years are the largest systems of caves in clay hitherto known worldwide. In this paper we provide the discovery of four new cave systems in a sector of the Black Bardena called gully of The Sorianos. The cavities explored are described and new data and details of biological and hydrogeological interest are provided. Its probable genesis and evolution is discussed.