1850.] EZQUERRA ON THE GEOLOGY OF SPAIN. 411 



mencement of the tertiary period, with the exception of some partial 

 modifications, for in general all the beds are in a horizontal position, 

 and Col. Silvertop only quotes along the coast of Andalusia some up- 

 heaved beds of the eocene period. It must, however, be observed, 

 that along the same shore there are some spots where the marine ter- 

 tiary formation attains, as at Cuevas de Vera and Sierra Almagrera, an 

 elevation of 900 feet, which gives rise to the question as to whether 

 the waters of the Mediterranean reached that height before the Straits 

 of Gibraltar were broken through, or whether the shore itself has been 

 partially upraised since that period. Amongst the numerous fossils 

 which are found on this coast, there are some species of moUusca of 

 a most extraordinary size ; in the vicinity of Cuevas de Vera are also 

 found entombed the remains of elephants, isolated and distributed 

 in particular directions, which were washed down by the streams into 

 the ancient sea, all proving the existence at that period of a more 

 tropical climate than existing at present in this district. 



Our tertiary marine formations cover almost without interruption 

 the whole shore of the Mediterranean, and even beyond the Straits 

 in the pro^dnce of Cadiz ; I am not sure whether they extend into 

 Portugal, although it is probable. This tertiary zone extends but a 

 short distance into the interior, except in the valley of the Guadal- 

 quivir, where it may be traced without interruption from Cadiz 

 and San Lucar, ascending the river, to Andujar and Liiiares, where 

 it rests upon granite, covering up the rich veins of galena which pene- 

 trate this plutonic mass of hills. On the northern slope the tertiary 

 beds are but slightly developed. In the interior I know of no ma- 

 rine tertiaries except in the neighbourhood of Burgos towards the 

 north, which must have been a salt lake at that period. In this for- 

 mation we find a few deposits of lignite, the most important of which 

 is probably that of Utrillas, near Montalvan, in the province of 

 Teruel. 



In the third volume of our *Anales de Minas,' published in 1845, 

 I have given a general account of the great lacustrine formations of 

 central Spain. The most important of all, and that which has been 

 best examined, is what I have called the basin of the Douro (Cuenca 

 del Duero), the surface of which is nearly forty Spanish leagues square, 

 — 3400 square kilom. To the west and south it rests on the crystalline 

 or metamorphic formations of Galicia and of the frontiers of Portugal, 

 of the Sierra d' Avila, and of the Guadarrama ; to the north on the 

 Devonian beds and on the chalk of the mountains of Leon ; and to 

 the east on the cretaceous beds. The lacustrine basin of the Ebro is 

 also very considerable, but I do not know its exact limits. It is, 

 perhaps, somewhat longer, follomng on both sides the course of the 

 river ; but it is not so broad. It rests almost everywhere on chalk, 

 and partly on the Jurassic beds. The basins of the Tagus and of the 

 Guadarrama are only separated from each other by ramifications of 

 the mountains of Toledo. The former, which is the most extensive, 

 is placed exactly in the centre of Spain, and includes the capital. 

 The fetid lacustrine limestone of Colmenar serves as well as the granite 

 of the Guadarrama for architectural constructions, and is also used 



VOL. VI. — PART I. 2 G 



