ON THE TERTIARY FORMATIONS OF SPAIN. S 



N. and N.E. the marls and gypseous beds are constantly capped by 

 beds of lacustrine limestone which continues as far as the Sierra de Peria 

 Orada, where it rests against the chalk and greensand formation. 



This tertiary basin, which may be called that of the Ebro, in addition 

 to what has been already said, is remarkable for its extent, its abun- 

 dant supply of water, the fertility of its soil, and its great elevation 

 above the level of the sea. The author has accompanied his remarks 

 with a map of the district round Burgos, on which he has roughly 

 laid down the principal geological features. 



The same volume contains an account of the geology of Estremadura, 

 and the northern parts of Andalusia, translated from the French of 

 M. Frederic Le Play. The following is an abstract of the remarks re- 

 lating to the tertiary formations. They occur on the northern flank 

 of the Sierra Morena, in the immediate vicinity of Cordova. The 

 most characteristic rock is an earthy shelly limestone, rather incoherent 

 and porous, containing many organic remains, chiefly Terebratulse and 

 others resembling those found in the island of Corcega, noticed by 

 M. Deshayes. 



These shelly limestones rest on a more ancient formation, consisting 

 of fine argillaceous marls of a grey colour, disintegrating easily, and 

 crumbling away under the influence of atmospheric action. Near the 

 town of Cordova it forms an escarpment 80 varas* thick, along the 

 face of which the beds generally appear to be horizontal, although 

 really inclining slightly to the S.S.W., dipping under the transported 

 matter of the third tertiary period which constitutes the greater part 

 of the lower plains of Andalusia. These marls resemble in outward 

 appearance the grey marls which accompany the gypsum of the Paris 

 basin. No organic remains have yet been found in them, although 

 it is probable that they exist, and that they belong to the same period 

 as those found in the shelly limestone which rises almost to the same 

 level on the opposite banks of the Guadalquivir. 



In the tertiary basin situated on the table-land which forms the 

 plain of Espiel, is also a limestone containing freshwater shells, which, 

 like those of the same character in other places, appear to belong to 

 the intermediate or miocene period of the tertiary formation. 



In the neighbourhood of Badajoz the Guadiana has cut its way 

 through a range of hills, in the escarpment of which is a series of 

 beds of grey marly limestone, penetrated by small cylindrical cavities. 

 Freshwater fossils, resembling those of the lacustrine limestone of the 

 second tertiary deposit, have been found in one or two places in the 

 escarpment. Further to the east these rocks pass, without any line 

 of demarcation, into one of a totally difl*erent character, probably sili- 

 ceous from its not effervescing with acids. After describing the dolo- 

 mitic rock in the neighbourhood of Badajoz, and the euphotide or 

 igneous rocks by which the crystalline dolomite has been penetrated, 

 the author comes to the conclusion that the dolomitic rocks are de- 

 rived from the metamorphism of the freshwater limestone by the agency 

 of the injected euphotide. 



The tertiary formations of the third period are described as con- 

 * The vara of Castille = 2-778 English feet. 



B 2 



