Yol. 55.] TOKSION-STKTJCTURE OF THE DOLOMITES. 667 



Any comparison which seems desirable to the reader can be made 

 independently ; more especially would 1 call attention to several 

 excellent photographs in the work just quoted. 



General form of the Groden Pass Anticline on the 

 west side of the Pass. — Approaching the Pass from the Groden 

 Yalley, the footpath for the ascent is reached at Plon (see General 

 Map, PL XL^). The rocks in the stream beside the Plon Inn are 

 fossiliferous Bellerojjhon-limestone strata. These Permian rocks are 

 succeeded by a disturbed succession of Lower Triassic(Seis and Campil 

 strata) and Muschelkalk horizons. The whole series represents an 

 anticlinal form which we may term the Groden Pass Anticline, 



The anticline is here greatly contorted, and split into two un- 

 symmetrical halves by a longitudinal fault directed west-south-west 

 and east-north-east, and to this reference will be made as the 

 Plon Fault. Minor transverse dislocations cross this longitudinal 

 fault : one of these is well exposed where it penetrates Seis Lime- 

 stone near a lateral waterfall, the limestone standing vertically. 



The strike of the rocks in the northern fault-block of the anticline 

 veers round from a north-westerly and south-easterly direction to 

 west-south-west and east-north-east; the general dip is northward 

 throughout, although the angle varies very frequently. The strike 

 veers round similarly in the southern fault-block, where the dip, 

 in spite of many small faults, holds southward. The crags and 

 steep pastures of Pitzculatsch Hill represent the southern fault- 

 block. They may be most conveniently examined by taking the path 

 from Plon towards the Sella Pass, and diverging from it towards 

 the numerous exposures on the hillside. 



The Pitzculatsch Pault-dyke. — When a height of about 

 1800 metres is reached on the path, a steep gully will be found 

 running up the hill, but it is practically hidden from the pathway 

 by fir aud brushwood. A dyke of igneous rock occupies the gully, 

 and follows the course of a vertical fault east-north-eastward to the 

 Groden Pass. Muschelkalk strata, more particularly the Mendola 

 Dolomite or upper horizons, are faulted on the north side of the 

 fault against Wengen strata, and on the south side towards Sella 

 (fig. 1, p. 568). 



Origin of the so-called 'Buchenstein conglomeratic 

 tuff' as a shear-and-contact breccia. — The strata on both 

 sides show marked effects both of shear-slip and of contact-alteration. 

 The rocks exhibit in a remarkable degree the result of mutual 

 metamorphism of the intrusive and stratified masses. I observed 

 here quite clearly that the so-called 'Buchenstein conglomeratic tuff' 

 or ' Buchenstein agglomerate ' has its origin as sheared and altered 



1 The redrawing of tbe author's coloured map and original illustrations for 

 reproduction in black and white was carried out by Miss E. M. R. Wood and 

 Mr. F. Eaw in the Research Section of the Geological Department of Mason 

 University College, Birmingham, with the result that few practical detail 

 have been lost, despite considerable reduction in size. 



