The Castilian bend of Rudolf Staub (1926): historical perspective of a forgotten orocline in Central Iberia

The existence of an orogenic arc in the Variscan belt of Central Iberia is traced from its first recognition by the Swiss geologist, Rudolf Staub, at the XIV International Geological Congress (Madrid 1926), to the present. A review of the literature exposes the main facts related to Staub's original interpretation, and its subsequent discussion, rejection and rehabilitation in the 21st century. The Castilian bend or Central Iberian arc is defined as a secondary orocline formed during late stages of the Variscan orogeny, with a curvature opposite to that of the better known Ibero-Armorican arc. It bends the older Variscan, structures, the magnetic anomalies, and the stratigraphic, metamorphic, and magmatic zonation of the Iberian Massif. The original NE-SW trend of these elements has been preserved by porphyroblast inclusion trails that maintained constant orientations during the formation of both oroclines. The rediscovery of the Central Iberian arc has given a new impulse to research in the Iberian Massif during the last decade, which we briefly review. A short discussion is also included of remaining unknowns regarding the precise geometry and formation mechanism of the arc, and the new perspectives it opens for future research in the Variscan belt.