^^^' 55'] GEOLOGY OF THE DAVOS DISTRICT. 383 



mountains of the Silvretta, Scaletta, Diican, and Albula groups, 

 from whicti flow tlie Landquart, Fluela, Dischma, and Sertig rivers. 



From a geological point of view the next question is, what posi- 

 tion do the valley and mountain-ranges bear to the general strike of 

 the strata of the whole country ? While the general trend of the 

 valley corresponds roaghly to the line of the Alpine axis, it will 

 be found that it does not follow exactly the strike of the rocks. 



The eastern mountains consist of crystalline schists and gneisses, 

 but these also cross the Landwasser and form part of the western 

 group. The limestones and dolomites of Parpan and Arosa can be 

 traced to Klosters, and thus the strike of the strata is more nearly 

 east-and-west than the geographical line of the Davos Valley. North 

 of Klosters there is an apparently abrupt change, and the outcrop 

 turns northward and westward : a band of limestone (easily trace- 

 able by the eye from considerable distances) running obliquely 

 north-westward across the Rhatikon, and finally merging into the 

 mountains of the western Arlberg. 



In the neighbourhood of Klosters we have thus on the west the 

 great mass of the grey Bundner Schiefer, and on the east a vast 

 thickness of crystalline rocks ; between them is a narrow band of 

 limestones and associated rocks widening out northward, but of 

 ouly slight thickness here, reappearing southward in the mountain- 

 ridges which form the subject of our study. 



The general dip of all these strata is southerly and easterly, and 

 as the crystalline rocks on the east are undoubtedly older than any 

 of the neighbouring strata, it is evident that there has been a great 

 overthrusting of the older strata over the newer from the eastern 

 side. 



It remains to be seen whether it is possible to trace out the 

 different elements of the complicated zone which lies between the 

 more uniform areas of the east and west. Before attempting such 

 an explanation, it is, however, necessary to form some idea of the 

 different rock-formations present within the district, their character- 

 istics in the field when typically developed, and the modifications 

 that they may under certain conditions undergo. 



II. The Eocks of the Disteict. 



In describing the rocks it will, perhaps, make matters clearer if 

 I refrain from attempting a stratigraphical sequence, but work 

 inward from the outer boundaries of the region towards the complex 

 area round which the more controversial questions centre. 



The whole series of rocks may be divided into two groups. In 

 the first (a) are included those which cover the greater part of the 

 map, and are more or less distinctly referable to certain great 

 geological systems. In the second group (b) may be included rocks 

 of limited distribution and doubtful age, occurring in a definite 

 relative position, though with a confused and sinuous outcrop. 

 These are the rocks which are found along the overthrust or 

 * Aufbruchszone ' of Steinmann, and in the Arosa district he 



