Structure of the Austrian Alps, fyc. 91 



the Schlossberg and the Erzberg, producing an upcast to the 

 south-east, in consequence of which the red sandstone and 

 red gypseous marl forming the base of the metalliferous dolo- 

 mites, are once more brought out, and the whole secondary 

 system is seen to rest unconformably upon inclined beds of 

 grauwacke passing, in some places, into a millstone conglo- 

 merate, in others, into a grauwacke slate which is here and 

 there calcareous, and contains subordinate, thin beds of dark* 

 blueish coloured limestone. 



In the calcareous grauwacke slate there are many stems of 

 encrinites ; and the beds of limestone contain innumerable fossil 

 shells chiefly of the three genera Producta, Spirifer, and Tere- 

 bratula. Hand specimens of these rocks could not be distin- 

 guished, either by their structure or by their fossils, from Eng- 

 lish mountain or transition limestone: and it deserves remark, 

 that in one of the sections below the village of Bleiberg, thin 

 calcareous bands full of transition fossils mark the dip and 

 bedding of the rock: while its slaty cleavage (precisely as in 

 some of the calcareous transition slates in the north of Eng- 

 land) is transverse to the stratification. 



The fossil shells collected by ourselves are : 



Producta hemisphaerica ; 



Producta latissima; 



Producta, a species resembling P. Martini ; 



Pecten, resembling a species in the transition series of Cork. 

 And to this list may be added, 



Encrinites, fragments of Spirifers, &c. &c. 

 These facts appear to decide the question respecting the age 

 of the system of beds we are describing, as far as regards the 

 country south of the central axis : and to place the correspond- 

 ing beds on the north side of the axis in a different system, 

 would be a violation of the plainest rules of analogy. It seems 

 therefore to follow, that certain important inferences, recently 

 drawn from the non-existence of transition rocks with organic 

 remains in some portions of the western Alps, have no appli- 

 cation to the eastern parts of the chain here described*. 



* By reference to M. Rengger's memoir in the Denkschriften der allge- 

 meinen Schweizerischen Gesellschaft (Zurich 1829), it will be seen that 

 transition rocks form an equally important band in a part of the western 

 Alps, and that on their southern or inferior limit they graduate downwards 

 from grauwacke slate into mica-slate and gneiss; whilst in an ascending 

 series they pass through iron ore deposits into red sandstone and conglo- 

 merate. So that in the western division of the chain, as well as in the 

 eastern, they separate the Alpine or Jura limestone (synonymous terms) 

 from the primary rocks. 



N 2 3. Red 



