410 JMR. A. V. JENNINGS ON THE [^"g- 1899, 



the limestone-band of the Cotschna, it remains to be considered 

 whether they can be correlated with the formations noted else- 

 where, or whether they belong to some geological series not yet met 

 with. 



Starting from the sonth, and bearing in mind the succession of 

 strata in the eastern folds, we should expect to find the older 

 crystallines of the Ddrfliberg followed by Casanna Schiefer. Such 

 is the case along the Mittelgrat, though the typical schists are 

 interrupted by the presence of a granite. Following it, where one 

 would normally expect the Verrucano, comes the serpentine, and 

 between this and the dolomite the series of problematic red-green, 

 calcareo-argillaceous beds. When, on further examination, one finds 

 that the green layers in this mixed ' Schiefer ' are obviously ser- 

 pentinous, often even containing easily recognizable diallage-crystals, 

 and when one remembers that on the Parsenn slopes above occur 

 flaggy limestones of the Mittelbildungen distinctly interstratified 

 with red schists, the conclusion inevitably suggests itself that 

 the whole series of ' Rothe u. 'Griine Schiefer' (the ' Sv.' of 

 Theobald's map) result here from the intrusion of a peiidotite or 

 basic magma through a series of calcareous and argillaceous 

 beds, representing in part the Mittelbildungen and in part the 

 Verrucano. 



Fragments of fine-grained, though still distinctly conglomeratic, 

 Yerrucano occur on the northern slopes of the Stutzhach, but I have 

 not found it in situ. It is, however, quite distinct on the same 

 horizon above Klosters. The finer-grained or red-shale variety of 

 the Verrucano is here predominant, and the red shales pass into 

 lenticular patches of red hornstone with radiolaria, which attain 

 their maximum on the top of the Cotschna ridge, but also occur, 

 together with typical Verrucano, on the Eastern Rhatikon. 



Similarly, the brecciated crystallines of Laret and the Parsenn 

 slopes, with the associated talc-granite and quartzite, seem to 

 indicate a secondary fold between the serpentine and dolomite in 

 which the Casanna Schiefer have been crushed and fractured by 

 pressure and lateral movement. 



If our idea of the structure of the fold is correct, we should 

 expect some of these formations to reappear on the northern slope 

 below the dolomite, with still more evidence of the forces that 

 have been at work, and it is precisely in this position that the two 

 breccias above described are found. 



The conclusion, therefore, seems forced upon us that these are 



true friction-breccias formed in situ ; that the upper one represents 



the lower limestones broken and, as it were, crushed into a paste 



of Verrucano ; and that the lower is the same band as the brec- 



' ciated crystallines of the Parsenn, corresponding to the Casanna 



^ Schiefer of the other folds. This view seems in direct opposition 



to the opinions of Steinmann, Tarnuzzer, and others who have 



. studied the breccias of different parts of Graubiinden ; but it is 



^ possible that those which they have regarded as derivative, and 



of Liassic or even Cretaceous age, may be on a different horizon 



from those of the Cotschna. 



