Vol. 55.] THE GEOLOGY OF THE DAT08 DISTRICT. 403 



The Third or Strela Fold. (PL XXVII & figs. 3, 5 & 6.) 



This I have called the Strela fold, as it includes the mountains 

 referred to by Theobald as the ' Strelagebirge ' : the Schiesshorn on 

 the south, and in succession northward the Thiejerfluh, Madrigerfluh, 

 Kiipfenfluh, and Schiahorner. 



It will be seen that near the Mayenfelder-Furka Pass this fold is 

 in close proximity to the western edge of the second fold, separated 

 from it only by the band of Verrucano which lies in the long 

 trough-like depression running from the Kiipfenfluh to the Sand- 

 hubel. This band seems to be the ' knee ' of the intermediate 

 anticlinal, the crystalline axis of the Korbshorn lying here below 

 the surface, though it is doubtless continuous with the similar rocks 

 near the Arosa Rothhorn. 



In this Strela fold the Mittelbildun gen are very greatly reduced, 

 and the great cliffs that overlook the Arosathal consist almost entirely 

 of Hauptdolomit. It is interesting to note that the crystallines of 

 the Korbshorn mass, running up as it were on the dip-slope of 

 the Kiipfenfluh, have not yet been entirely denuded from its summit, 

 and thus the gneisses and schists of the Wannengrat actually cap the 

 dolomite-ridge for some distance. 



On the Strela Pass itself the stony waste will be found to contain 

 numerous fragments of the Lithodendron-kalk. Of its position 

 in situ, I am not very sure, but it seems to be a crushed infold of the 

 strata noted on the western peaks of the Ducan group. 



The sharply-tilted rocks of the Great and Little Schiahorner, with 

 their precipitous northern aspect, indicate the approach to a region 

 of still greater disturbance, while at the same time the rapid 

 thinning-out of the beds becomes evident from the marked change in 

 the scenery. Following the general line of strike northward and 

 eastward, one might expect to see another ridge of calcareous crags 

 stretching away by the Hornli towards the Silvretta, but nothing 

 of the kind is visible. The lower plateau of the Little Schiahorn 

 dwindles away to a narrow limestone-band (bordered by Verrucano), 

 curving round behind Davos Dorf, and there vanishing below the 

 superficial accumulations that fill the valley. 



On the opposite side, however, at the foot of the Seehorn, there 

 is again a patch of dolomite continuous with a band on the east 

 side of the lake. Theobald recognized the continuity of this with 

 the Schiahorn band, but the matter is so much clearer now, owing to 

 the railway-cutting, and is of so much importance to a right under- 

 standing of the north-eastern part of the area, that it is necessary 

 to note certain features in greater detail. (See fig. 3, p, 402.) 



At the point at which the railway nears the foot of the Seehorn, 

 the solid rock that rises from the valley-alluvium, and forms the 

 glaciated slopes on which the Easier Sanatorium stands, consists, 

 mainly at least, of Casanna Schiefer. Where the line cuts the 

 great roche moutonnee, a little farther on, the rock is seen to be 

 a fine gneiss or micaceous schist with characteristic black and 

 ochreous patches, evidently continuous with the band which is 



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