418 P. W, Sfuart-Menteafh — Ap2)endi.r to Pyrenean Geology . 



outcome. The question for every practical geologist is to find how the 

 error comes in. Is the stratigraphy hastily assumed on fragmentary 

 data ? Are the sections only * coupes perspectives ' ? Does the rest of 

 the Pyrenees warrant another explanation ? Are the Hippurites, with 

 their accompanying forms of a similar fauna, decisive of certain age? 



On the last question I may remark that I determined the best 

 specimens of these Hippurites at Miegebat in 1885, and was hence 

 denounced for twenty years, and my Upper Cretaceous figured as 

 Cambrian, along over fifty miles of the official map ; whereas fossils 

 that do not touch the problem are eagerly quoted since the wind has 

 changed. 



The one point certain regarding the Hippurite limestone is its 

 subordination to that "Austrian Flysch or TVmier Sandstein^' which 

 I detected in 1881, and which is now accepted as a main element of 

 the Pyrenees. All the fossils of this formation, named and classed in 

 the museums of Austria, Italy, and Switzerland, are repeated in the 

 Pyrenees, and have been of notoriously doubtful value for half a 

 century. Hippurites have been scarcely less puzzling, and have been 

 cited by Darwin in the Jurassic and by most authorities as peculiar to 

 the Turonian. At Eaux Chaudes I have proved the base of the 

 anomalous limestone to be Cenomanian by Ostrea flaheUata, Janira 

 quinqiiecostata , Sciosia, Ostrea cf. carinata, and various corals ; but its 

 base at Gavarnie is Campanien, on the excellent authority of 

 M. Douville. Thousands of years should consequently have elapsed 

 between its deposition at these two points of an identical sheet. 



The final and most elaborate sections of M. Bresson are those of Eaux 

 Chaudes, in his desci'iption of the meeting of the Societe Geologique 

 of 1906. The point most contrasting with my section of the same 

 Bulletin of 1893 is his figure of the Arrioutort, represented as an 

 overlying syncline. Numerous visits to that point have assured me 

 that the Hippurite limestone is there the termination of a long wedge 

 running north and south, and descending almost vertically to the 

 bottom of the neighbouring valleys. As in the single case which 

 I showed Mr. Dixon at La Prade, the limestone figured by M. Bresson 

 as a flat platform is in deep and narrow synclinal wedges descending 

 to beneath the valley bottoms. Such wedges are a special feature of 

 the western Pyrenees, and have the very peculiar property of abruptly 

 changing their direction at right angles. MM. Fournier, Termier, and 

 Bresson all attest this fact in their latest mappings. Its effect is to 

 produce an appearance of underlying Cretaceous exposed by valley 

 erosion. I have traced it to the filling of ancient gulfs or valleys, and 

 hence compared the case to that of Gosau. At Camarasa, and much 

 of Catalonia, the gypseous Oligocene runs vertically downwards to the 

 bottom of such valleys. At Salies du Salat, M. Leon Bertrand has 

 maintained that the Trias has glided along the surface of even the 

 Oligocene, and has moulded itself on an ancient valley to a depth of 

 over 1,300 feet, proved by borings that indicate horizontal bedding. 

 JN^ormal deposition in valleys is less complicated. At Gavarnie and 

 Eaux Chaudes the continual formation of hard travertin filled with 

 transported fossils is a common source of error, and, when submarine 

 and followed by dislocation, involves unsuspected sources of illusion. 



