p. W. Stuart- Menteath — The Age of Fyrenean Granite. 539' 



abandoned by M. Carez as untenable ; and the suggestion that some 

 other name might be given to the granite is inconvenient, seeing 

 that the rock in question has been recognised as granite during more 

 than a century by every observer who has seen it. 



My position in the matter differs from that of geologists w^ho feel 

 called upon to explain away what they suppose to be an exceptional 

 anomaly. Since 1866, when I first studied these rocks during more 

 than two months at Bagneres, I have traced the same phenomena 

 throughout the Pyrenees. Around Leyrisse one sees merely a 

 normal and usual feature of the Flysch, as I have studied that 

 formation from St. Jean de Luz to the Corbieres. One sees com- 

 pletely exposed at Leyrisse a peculiar and complex mechanism of 

 intrusion, eruption, and metamorphism, whose several features are 

 unerringly recognisable in obscurer sections after the field-practice 

 of many years. Its presence is verifiable in a single excursion at 

 Leyrisse, but in some other cases has been only rendered certain by 

 the patient researches and happy accidents of twenty years. Clearly 

 conclusive sections and ample indications are now known to me 

 along the entire Pyrenees. Along the hundred kilometres between 

 Leyrisse and Iholdy the granitic penetrations of the Flysch are 

 especially extensive and clear. Here rises the vast granitic 

 intrusion between Iholdy and Cambo, which all recent textbooks 

 assume to be of Archaean age. All observation, from Dufrenoy to 

 my minutest mappings of the district, prove this granite to be as 

 Cretaceous as its indubitable continuation to the east. 



Between Suhescun and Iholdy, three miles to the south-east of 

 the granite outcrop, the undisputed Flysch, mainly of white marl 

 abounding in characteristic fucoids, forms a lofty ridge visibly seated 

 on the same fossiliferous Cenomanien which similarly supports the 

 Flysch elsewhere. Above this limestone, and in alternation with 

 regular beds of white marl dotted with fucoids, one finds a series of 

 great lenticles of angular bi^eccia, mainly of ophite and quartzite, bub 

 including limestone, slate, and some fragments of granite and gneiss. 

 Blocks of three to four yards in diameter of ophite and quartzite are 

 conspicuous. These beds amount jointly to about 2,000 feet in 

 thickness. They are clearly in every detail a repetition of the 

 peculiar mechanism of Leyrisse. The ophitic character and com- 

 position are merely more prominent at this point; whereas at 

 Leyrisse and to the west of Iholdy the granitic form predominates. 

 Around Leyrisse the ophitic form of the same mechanism is frequently 

 visible and soon predominant. At Iholdy the breccias pass into 

 solid masses of ophite, and can in every detail be traced as eruptive 

 intrusions traversing the Cenomanien limestone, and both traversing 

 and feeding the sedimentary beds of the Flysch. No other 

 explanation will fit the phenomena of Leyrisse and of the entire 

 intermediate Flysch. I first discovered and classed the Pyrenean 

 Flysch through familiarity with that of Greece, Italy, and Austria. 

 Th. Fuchs classed that Flysch as of eruptive origin. Even in the 

 Alpine Flysch the Taveyannaz Sandstone has been recognised as 

 eruptive, and as analogous to Pyrenean ophites, by the only German 

 geologist who has compared the two. 



