12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



a complex thrust, composed apparently of two related planes, which 

 had been folded back upon itself in a later movement from the oppo- 

 site direction. The later movement had also resulted in a thrust, dis- 

 locating the former one and superimposing the Jurassic and Triassic 

 strata of the Rocher Pourri and the Rocher Plat upon the Eocene and 

 the Rhetic mass infolded in it. To the southeast of the Rocher Plat 

 we crossed another fragment of the Breche de Chablais-Hornfluh, 

 also superimposed upon the Flysch by thrusting from the northwest, 

 and observed that the thrust plane was closely folded and cut off by 

 the Jurassic of the Gummfluh, again overthrust upon it by the later 

 movement from the southeast. ( See the sections in Jaccard's paper, 

 pis. 36-38.) 



The structure involves one thrust plane from the northwest and 

 two later parallel thrust planes from the southeast. The strata in- 

 volved in the movements have also been closely folded. 



This structure is one of the most complex I have ever seen, and I 

 could not have understood it, as I believe I do, had I not been pre- 

 pared by the observations on folded and intersecting thrusts which I 

 had made at the northern base of the Wildstrubel, in the Laufboden- 

 horn, etc. During the two days that I was guided by Dr. Jaccard, 

 between Chateau d'Eux and Zweisimmen, I saw repeatedly the evi- 

 dence of older thrusts from the northwest and of younger thrusts from 

 the southeast intersecting and dislocating them. 



In the tete plongeante of the Pte. de Cananeen we have an excellent 

 illustration of the structure of those masses which were described by 

 Querreau and later by Prof. Lugeon as being isolated and " without 

 roots." To satisfy myself on this point, I studied the Mythen above 

 Schwyz, and the Breche de Hornfluh near Zweisimmen. I have no 

 doubt that these masses and others described by Prof. Lugeon, includ- 

 ing the Breche de Chablais, are actually underlain throughout by 

 younger strata and are without any connection with the like forma- 

 tions in place. It is well known that some of these isolated masses, 

 those of the Klippes, are " exotic " ; that is to say, no strata of the same 

 facies have ever been found in place. Hence, it is supposed that 

 they must have come from a distant zone south of the Alps. An 

 earlier and, I think, a more correct view was that they came from 

 strata deposited in the zone of the Prealpes, where they are now found. 

 That view was discarded because there was no explanation of the man- 

 ner in which these isolated masses might have risen through and have 

 become superimposed upon the younger (Eocene) strata which now 

 so widely cover that zone. But let us consider the mechanical effects 

 of intersecting thrust planes. 



