Structure of the Austrian Alps, fyc. 87 



ful chloritic slate; alternating here and there with thin bands 

 of light blue and green, laminated and granular limestone, 

 somewhat resembling the cipollino of the Italians ; sometimes 

 also alternating with thin quartzose bands, identical with the 

 beautiful green, quartzose, slaty masses which abound in a 

 corresponding part of the pass of the Brenner. . With the 

 beds of the Katsberg terminates what we consider the pri- 

 mary system of our transverse section. It is not however 

 possible to draw any precise line of demarcation between 

 this and the superior transition system ; for here, as well as in 

 the valley of Gastein (see PL II. fig. 1, 2), the two classes of 

 rocks seem, through the intervention of chloritic schist with 

 thin bands of limestone, to pass insensibly into each other. 

 We have thought this fact worth stating, although it is pro- 

 bably a mere local accident of structure, and of no real im- 

 portance in the history of the successive formations*. 



2, Crystalline Rocks containing calcareous Beds 'with traces of 

 organic Remains, graduating into Rocks conforming to the 

 ordinary Transition Type, 8?c. fyc. 



The prolongation of the section over the Tauern Alp, from 

 St. Michael on the Mur to Radstadt on the Enns, is through 

 the lower transition system of the Alps. Near St. Michael, 

 beds similar to those of the Katsberg alternate with large 

 masses of crystalline limestone ; and for some miles north of 

 that place, the abundance of limestone among the other cry- 

 stalline rocks begins to give a new character to the country. 

 In our passage through it, we however thought that we were 

 still in the primary system of the chain ; and we can hardly 

 express the surprise we experienced when we first discovered, 

 near the village of Tweng, mica-slate with garnets, and chlo- 

 rite-slate with thin layers of white crystalline limestone, alter- 

 nating with, and passing into a more thick-bedded limestone, 

 part of which was of a dark blue colour, of less crystalline 

 texture, and contained many encrinital stems. 



In ascending the mountain above the last-mentioned vil- 

 lage, we found the same dark-coloured encrinite-limestone 



* In using the terms primary and transition, we have only endeavoured 

 to conform to the language current among geologists. The two classes of 

 rocks cannot, perhaps, in any case be precisely separated from each other. 

 It is true that among the stratified rocks of a considerable part of the 

 central axis there are no traces of organic remains : but they may once 

 have existed, and have been obliterated by subsequent crystalline action : 

 and the central peaks of true granite are (at least in their present form) 

 probably among the most recent mineral masses of the chain. 



repeatedly 



