370 E. E. L. Dixon— The Gavaniie Overthrust, 



4. Carez draws a similar conclusion from the fact that although 

 Jurassic and Lower Cretaceous rocks are absent from Gavarnie, etc., 

 they are represented to the north, at one place at a distance of a mile, 

 by more than 2,000 metres of rocks (compact limestones, etc.) ■which 

 were " certainly deposited far from a coast-line." [This argument is 

 a variation of the preceding. When Carez remarks that everywhere 

 in the southern region the Campanian rests on Palaeozoic rocks he 

 overlooks the fact, previously pointed out by Bresson and others, that 

 in that part of the region which lies in Spain it is separated therefrom 

 by Permo-Trias. On Carez' view this is explicable only on the 

 supposition that in that district his overthrust separates the Campanian 

 from the Permo-Trias, a point to which we shall return later. The 

 discordance at the base of the Campanian to which he alludes has 

 been explained bj- the above authors as the result of a widespread 

 hydrocratic movement. This view is much more probable than Cai'ez', 

 which involves the supposition that a thrust-plane has persisted at one 

 horizon throughout its visible extent of many miles.] 



5. As it is difficult to follow Carez here 1 will quote his argument 

 in full (pp. 1157-8): "La difference d'altitudc actuelle entre les 

 depots cretaces de la crete frontiere et eeux de la plaine [septentrionale] 

 depasse 8,000 metres. Or, si le Campanien n'a pas le meme facies 

 dans les deux zones, en revanche le Danien est identique, tant au point 

 de vue de sa composition petrographique que de sa faune. Leymerie 

 avait deja ete frappe de ce fait, et il en avait conclu, avec raison, que 

 le soulevementde la zone frontiere etait posterieur au depot du Cretace 

 qui la constitue. C'est ce qui me parait demontre : les fossiles daniens 

 ne vivaient pas a Montgaillard et dans la Haute-Garonne sous une 

 profondeur d'eau de plus de 3,000 metres, et cette colossale difference 

 d'altitudc entre des sediments identiques est indubitablement le resultat 

 de mouvements posterieurs a leur depot." [Undoubtedly, but as 

 a whole series of mountain-structures of Tertiary age separates the 

 two areas where contemporaneous deposits differ in altitude by 

 3,000 metres, it would seem that this difference of level demands no 

 further explanation.] 



6. After referring to the gentle inclination of the Campanian sheet 

 and to the Tertiary age of the principal orogenic movement in the 

 Pyrenees, Carez asks, "How explain, on the theory of deposition in 

 place, that this gigantic movement has not affected the Cretaceous 

 rocks?" [As already pointed out by Bresson, the Cretaceous sheet is 

 folded or sheared at several places, phenomena which are doubtless 

 connected with the Tertiary overthrust of Palaeozoic I'ocks from the 

 north, previously described. On the whole, however, it is undistorted, 

 a fact which is not only difficult of explanation on the hypothesis that 

 the Cretaceous sheet has been overthrust in the opposite direction to 

 that taken hj the overlying Palaeozoics, but is readily explicable if we 

 regard the sheet and its basement-platform as part of the base of the 

 plateau-blocks of the Spanish side, which has been buried, over an 

 area of many square miles, beneath the overhipping northern rocks. 

 Again, the Permo-Trias beneath the Cretaceous sheet in the valley of 

 Hount-Sainte cannot, in the absence of any internal or external 

 evidence of movement, be supposed to have been overthrust, as it is 



