368 E. E. L. Dixon — The Gavamie Overthrusf, 



recent publications on the Pyrenees.^ In the first two, Mr. Stuart- 

 Menteath, unfortunately, introduces disparaging references to Darwin 

 and others, which are as germane to the case as "the flowers that 

 bloom in the spring," and only serve to repel proper consideration of 

 his other contentions. These last are directed against the degree to 

 which the theory of overthrusting has been pushed in the Pyrenees, 

 for he maintains that in the western part of the range (feuilles de 

 Bayonne et de St. Jean-Pied-de-Port) gigantic overthrusts have been 

 invoked in order to explain anomalies which do not in reality exist, 

 as they arise from the incorrect identification of various outcrops. 

 He particularly challenges some of Termier's conclusions. As Termier 

 has cited- as corroborative evidence the existence at Gravarnie of 

 a charriage which has ' carted ' the Upper Cretaceous from the 

 Spanish side across a strip of country 200 kilometres long, a con- 

 sideration of the latter instance is evidently of more than local 

 interest ; as Termier says "... s'il y a charriage, le phenomene 

 est general et embrasse tons les depots cretaces, de part et d'autre, de 

 I'axe pyreneen, et meme toutes les Pyrenees." 



To Carez is due this view that the Cretaceous at Gavarnie has been 

 thrust from the south over the crj'stalline rocks on which they now 

 rest. Stuart-Menteath, Bresson, and others, have maintained that the 

 hippurite-limestone of the Gavarnie district is in its original position 

 relative to the platform below. In the work previously cited, though 

 the Palaeozoic rocks are shown by Bresson to have been thrust over the 

 Cretaceous from the north, the latter is stated to be in place because 

 its basement-bed contains not only pebbles of quartz and, occasionally 

 (op. cit., p. 247), of the subjacent schists, but also a littoral fauna 

 (ovsters, etc.). He apparently regards the even plane on which it 

 rests as worn down by the Cretaceous sea. Carez, on the other 

 hand, gives nine reasons, under the following heads, for regarding the 

 Cretaceous as overthrust from the south : — ^ 



1. Absence of any literal band at the base of the Cretaceous. 



2. Existence of an even, planed surface, forming the ' substratum ' 

 of the Cretaceous. 



3. Absolute difference of facies between the Cretaceous of Gavamie 

 and neighbouring places, and the beds of the same age in the northern 

 plain. 



4. Absence of the Jurassic and the Lower Cretaceous at Gavarnie. 



5. Impossibility of admitting the simultaneous deposition of the 

 Upper Cretaceous at Gavarnie and in the northern plain. 



6. Almost horizontal position of the Cretaceous of the frontier. 



7. Priority of the folding of the rocks of the 'substratum' to the 

 attainment by the Cretaceous of its present position. 



8. Junction by a fault of the Palaeozoics and the Cretaceous at 



1 P. W. Stuart-Menteath : " Sur les Methodes de la Nouvelle Geologie," 1907 ; 

 "La Xouvelle Geologie a Biarritz" (Extrait de ' Biarritz- Asf?ociation ') , pts. 1 and 

 2, (1907 and 1908). P. Termier, "Sur la Structure Geologique des Pp-cnees 

 occidentales," C,R. Ac. Sc, tome cxli (1905), p. 966. L. Ca'rez, " Geologie des 

 Pyrenees francjaises," Mem. Carte Geol. Fr., fasc. i-iv (1903-0). 

 "2 Op. cit., p. 966. 



3 Op. cit., tasc. ii (feuilles de Tarbes et de Luz) (1904), p. 1156. 



