In the hinterland the Palaeozoic Sierras trend finally to the north-west, washing the Hercynian axial lines which curve into this direction from both the Sierra de Toledo and the Sierra Mo rena. At Montoro the course of the Guadalquivir has been im posed on the Palaeozoic by the removal of overlying Tertiary formations. East of Almaden the Palaeozoic is pierced by Quater nary basalts of the Campo de Calatrova beyond which tongues of Mesozoic projecting from La Mancha bring the Guadiana drain age into the Palaeozoic area.
in the Torres Vedras area. Jurassic limestones sketch the struc tural skeleton of the Mesozoic fringe of the Meseta. In the Mon dego region, a Jurassic upf old, flanked on two sides by Turmian formations, runs west–south-west to Soure and then west–north west to Cape Mondego by Verrede and Buarcos. This axis de limits on the south an area of worn Cretaceous reliefs above which stand out the Jurassic of Contanhede separated from the sea by a broad belt of high dunes. The Cretaceous, which appears in depressions along the principal axis as well as on the flanks of the Jurassic zone, is widely developed in the Cintra region where the Jurassic scarcely emerges. South of the Tagus river move ments of Alpine date have brought up the Jurassic to form the higher parts of the complicated Sierra Arrabida which runs west– south-west to Cape Espichel. In Algarve the Lias and Jurassic, with a fringe of Cretaceous towards the littoral, are folded against the southern edge of the plateau and contribute granite and lime stones to the complexity of the zone.
The lower Carboniferous rocks of Spain consist partly of lime stones and partly of sandstones and conglomerates like the culm of Devonshire. It is in the culm of the province of Huelva that the celebrated copper mines of Rio Tinto are worked. The Upper Carboniferous is formed, to a large extent, of sandstones and shales, with seams of coal; but beds of massive limestones are often intercalated, and some of these contain Fusulina and other fossils like those of the Russian Fusulina limestone. In the Cam brian and Silurian areas of the north-west, Tertiary movements have probably compressed the strata in the arc of the western Asturias, but not in the Carboniferous area to the east where the Carboniferous has its most extensive development in Spain, covering a considerable section of the eastern Asturias, and ex tending more or less continuously through the provinces of Le6n, Valencia and Santander.
The blue-grey mountain limestone of the lower Carboniferous form the triple massif of the Picos de Europa and the crests of many sierras. The culm, which also forms mountains, especially along the upper Deva, marks the transition to the continental conditions in which originated the sandstones and slates of the middle Carboniferous, with their intercalated beds of coal, princi pally the beds of the Tangres and Mieres basins. Tertiary move ments raised the Carboniferous along an east–west axis to form the Cantabrian chain.
To the north of the Carboniferous of the central Asturias lies an area of Mesozoic marine invasion with deposits in a belt trending east and west behind the Palaeozoic "island" by the Cabo de Penas district. From Pena Prieta eastward the altitude of the summits of the Cantabrian chain declines and the Cre taceous is rapidly substituted for the Carboniferous. In the half circle between Pena Tabra and the Sierra de Alcaraz the Meseta is bordered by highlands principally of Mesozoic formations. The tectonic relations between these highlands and the Cantabrian system, which continues eastward in the Cretaceous to the Pyre nean front, is not clear.
The Permian is probably represented by some of the red sand stones, conglomerates, and slates in the Pyrenees, in the Sierra de Cuenca and in Andalusia. The Triassic system is well-developed in the north of the peninsula along the Cantabrian chain and east wards to the Mediterranean. It is composed of red and varie gated sandstones, dolomites, and marl, and contains deposits of gypsum, aragonite, and rock salt. The Jurassic overlies these strata and is especially important in the eastern part of the penin sula between Castile and Aragon, along the Mediterranean border, in Andalusia, and on the flanks of the Pyrenees. The early Juras sic conglomerates and grits are followed by limestones, some dolo mitic variegated marl, and overlying spongy limestones or dolo mites. The neritic Lias and Jurassic are important only on the borders of New Castile.