Abstract The Iberian Peninsula comprises the most extensive outcrops of Ordovician rocks in Europe. They are mainly situated within the different ‘zones’ of the Variscan Iberian Massif (also referred to as the Hesperian Massif), except the South Portuguese Zone, as well as in the Palaeozoic massifs of the Iberian Cordillera (an isolated part of the Iberian Massif), the Catalonian Coastal Ranges, the Pyrenees and the Betic Cordillera (Fig. 4.1 ). Geological sketch map of the Iberian Peninsula showing the distribution of Ordovician rocks (in black) with reference to the main Precambrian and Palaeozoic exposures (stippled). Key: A–G, Hesperian (Iberian) Massif: A, Cantabrian Zone; B, West Asturian-Leonese Zone; C, Iberian Cordillera; D, Galicia–Trás-os-Montes Zone; E, Central Iberian Zone; F, Ossa Morena Zone; G, South Portuguese Zone (dotted lines indicate zone boundaries); H, Betic Cordilleras; I, Catalonian Coastal Ranges; J, Pyrenees. 1–42, Main Ordovician reference sections and fossil localities in Spain: 1, Cabo Peñas; 2, ‘folds and nappes region’; 3, Sueve area; 4, Rececende and Villaodrid synclines (Mondoñedo Nappe); 5, Los Oscos thrust-sheet; 6, Vega de Espinareda synclinorium; 7, Caurel–Peñalba syncline; 8, Castrillo syncline; 9, Eastern Iberian Chains; 10, Albarracín anticlinorium (Western Iberian Cordillera); 11, Serranía de Cuenca anticlinorium; 12, Cabo Ortegal area; 13, Sil and Truchas synclines; 14, Alcañices synclinorium; 15, Guadarrama area (eastern ‘Central System’); 16, Verín-Bragança region; 17, Tamames syncline; 18, Sierra de San Pedro and Cáceres syncline; 19, Cañaveral-Monfragüe syncline; 20, Guadarranque syncline; 21, Herrera del Duque syncline; 22, Corral de Calatrava syncline; 23, Almadén syncline; 24, Torre