270 P. W. Stuayt-Menteath—Salt Deposits of Bax, etc. 



Logrono along the Spanish side of the Pyrenees are clearly deposited 

 from evaporated lagoons formed during the uprise of the chain 

 in Tertiary times. The salt deposits of the French Pyrenees are 

 of a more local and varied character. There is a general contrast 

 between the two series which reflects the general contrast between 

 other features of the two slopes. In the salt deposits of the Pyrenees 

 one finds eveiy variety of lagunar character on the Spanish side, 

 and every variety of tectonic and local character on the French side. 

 Among the French deposits one may trace actual craters of explosion 

 filled with salt, old valleys filled with spring deposits, and small 

 accidental hollows that have preserved patches of salt water in 

 rising from the sea. Sunk valleys, like the Gouf de Capbreton, 

 have naturally preserved sunk deposits, when buried beneath 

 Tertiary accumulations ; and the ancient surfaces of the Cretaceous 

 formation and of the Oligocene land ai'e naturally marked by such 

 vestiges of their irregular uprise from the sea — especially where 

 the innumerable igneous bosses, that have visibly traversed the 

 Upper Cretaceous of the Pyrenees, have roughened the surface and 

 given rise to later fracture and irregular denudation. As salt and 

 gypsum can only resist solution under peculiarly favourable circum- 

 stances, it is certain that such solution must have produced extensive 

 dislocation. In the mountains of Persia and South America, gypsum 

 is over 1,000 feet in thickness across distances of over 50 miles. 

 No borings have yet fathomed the salt and gypsum of the Pyrenees, 

 although 1,082 feet has been reached at Salies du Salat without signs 

 of change. Such facts are a mere suggestion of what observation 

 might yield if not referred to one current theory. 



Not only the whole of the varied phenomena in question, but 

 even such local chemical productions of gypsum in the Flysch as 

 are visible near Biarritz at Croix d'Ahetze and elsewhere, have been 

 treated as characteristic of the Trias formation. In the Alps, as in 

 the Pyrenees, the gypseous beds of the Trias have been credited 

 ■with all the salt and gypsum of later beds of every age. The 

 stratigraphy which results from attempting to unite Oligocene and 

 Triassic beds into one formation is naturally astounding. 



Eound Biarritz, more conveniently than at Dax, the diversity of 

 the gypseous and red clays classed as Trias by Parisian geologists 

 may be verified. At Laduch, west of Villefranche, the fossiliferous 

 base of the Cretaceous may be seen resting on the gypseous marls 

 of the Villefranche salt-mine. At Caseville similar red clays, with 

 ophite and gypsum, are distinctly intercalated between the 

 fossiliferous Danien and Lower Eocene, and at Fontarabia they are 

 inclined at only 15° to the horizon. Beside the Negresse Station 

 the red brick-clay, of post-Glacial age, is now largely worked, and is 

 above the Glacial Diluvium that descends to the level of the lake, while 

 over it there is nothing but the modern blown sands of the spurious 

 Pliocene man. At Croix d'Ahetze the similar gypsum and clays, 

 formed by decomposition of iron pyrites in the Flysch, thickly 

 cover the almost horizontal surface of a quarried sheet of fucoidal 

 Flysch limestone. All the diverse formations thus enumerated, as 



