Abstract The area of western Montes de Toledo to Guadalupe boasts a thick succession of mainly siliciclastic sediment spanning terminal Ediacaran to lower Cambrian strata as indicated by a relatively sparse but diverse palaeontological record. A terminal Ediacaran age is based on the occurrence of Cloudina in platform carbonates of the lower part of the Ibor group and in correlative levels of olistostromes at the base of the Río Huso group. Higher in the Río Huso group are found trace fossils which indicate a Cambrian age, notably Treptichnus bifurcus , which overlaps the local stratigraphic range of macroscopic carbonaceous disc-shaped fossils identified as Beltanelliformis . Strata underlying the Río Huso group contain treptichnids. The fossil record of the terminal Ediacaran–Lower Cambrian of this area is in part comparable to Cloudina -bearing sediments from other regions, in particular Namibia, where treptichnid trace fossils also overlap the range of Cloudina . The possibility of a wider biostratigraphic significance of this should be further tested, including its relation to the base of the Cambrian.

Abstract The Iberian Peninsula has some of the most extensive Cambrian outcrops in Europe ( Lotze 1961 c ), including a diverse, continuous record of fossils and facies, and is thus a fundamental source of biostratigraphic information for the Cambrian System and its intercontinental correlations. Most exposures of Iberian Cambrian rocks occur in the Iberian Massif, but they are also known from the Pyrenees, the Catalonian Coastal Ranges and the Iberian Ranges (Fig. 3.1 ). Many exposures are geographically isolated and/or show tectonic boundaries, and facies changes are common, and these characteristics have led to a profuse stratigraphic nomenclature (see Fig. 3.2 ; Zamarreño 1983; Liñán et al . 1993 a ). Following Lotze (1961 c ), however, the Cambrian sequence can be overviewed as a diachronous Lower to Middle Cambrian carbonate sequence sandwiched by silici-clastic successions (Fig. 3.2 ). The lower of the siliciclastic units is entirely Lower Cambrian, whereas the upper unit ranges from upper Lower or Middle Cambrian to Upper Cambrian (Fig. 3.2 ). The Lower Cambrian series has been subdivided into the Corduban, Ovetian, Marianian and Bilbilian stages, and the Middle Cambrian series subdivided into the Leonian, Caesaraugustan and Languedocian stages (Fig. 3.2 ). The Precambrian/Cambrian boundary stratotype was erected by the International Subcommission on Cambrian Stratigraphy (ISCS) at the Fortune Head section in eastern Newfoundland (Canada) with the first appearance datum (FAD) of Phycodes (= Trichophycus) pedum ( Landing 1994 ). This FAD coincides with behavioural changes, increased

Abstract Outcrops of pre-Mesozoic rocks in Spain form various massifs that relate to both Variscan (Late Palaeozoic) and pre-Variscan tectonic settings (Fig. 9.1 ). The largest one of these is the so-called Iberian Massif, an autochthonous massif across which an almost complete, undisturbed geotraverse of the European Variscan orogen has been preserved. Other massifs occur as variably reworked basement complexes in Alpine chains. These are: (i) the various pre-Mesozoic massifs of the Iberian and Catalonian Coastal ranges, that can basically be considered autochthonous with respect to the Iberian Massif; (ii) the basement massifs of the axial zone of the Pyrenees; and (iii) parts of the internal zones of the Betics. The latter two are essentially exotic with respect to the Iberian Massif. Several tectonic syntheses have been published so far on this orogen (e.g. Matte 1986 , 1991 ; Julivert & Martínez 1987; Dallmeyer & Martínez-García 1990; Martínez-Catalán 1990 a ; Ribeiro et al . 1990 c ; Quesada 1990 b , 1992; Quesada et al . 1991; Shelley & Bossière 2000 ). It is agreed that the European Variscan belt resulted from the oblique collision and interaction between Palaeozoic supercontinents (Gondwana, Laurentia and Baltica) and a number of continental microplates during Neoproterozoic through Palaeozoic times. These microcontinents included fragments of magmatic arcs formed previously during a process of continental convergence at the margins of the major Neoproterozoic continental masses. Such a process resulted in the so-called Cadomian, Avalonian or Pan-African orogeny, developed

Abstract The Iberian Massif provides the largest outcrop of Variscan and pre-Variscan rocks in Europe (Fig. 2.1a ). It has been divided into several zones (Fig. 2.1b ) and, within the Spanish part of these zones,extensive areas are occupied by Precambrian rocks (Fig. 2.1c ). These Neoproterozoic successions are known under informal and local stratigraphic names so that it is not easy to provide a comprehensive synthesis of the Precambrian in Spain to a wide audience. Additional difficulties arise because different authors have focused their attention on different aspects (stratigraphy, petrology, tectonics, etc.) in widely separated geographic areas. Furthermore, widespread overprinting by Palaeozoic igneous and medium- to highgrade metamorphic processes has erased much sedimentological data and obscured correlations within and between Precambrian areas. As a consequence, many different local names have been proposed for stratigraphic units that are partially coincident with units in other localities. Thus, readers unfamiliar with geographic names may become discouraged when trying to compare and understand Precambrian stratigraphy from area to area in the Iberian Massif. To help readers, the names of the stratigraphic units and correlations across the zones are summarized in Figures 2.2 and 2.3 . Correlation chart of lithostratigraphic units from the Upper Neoproterozoic–Lower Cambrian in the different zones of the Spanish Iberian Massif. The Neoproterozoic–Cambrian boundary according to Bowring & Erwin (1998) . U-Pb isotopic data after Lancelot et al . (1985) , Schäfer et al . (1993) , Ordóñez (1998) , Fernández Suárez

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