﻿600 DR. A. P. YOUXG ON THE STEAIIGEAPHY AND [jN'oV. I908, 



arrangemeDt, and of tourmaline, they approach in character the so- 

 called ' older phyllites,' from which they are distinguished by their 

 finer grain. The induration and the fine puckering of some calca- 

 reous rocks associated with this group are no doubt due to contact- 

 alteration by the neighbouring igneous rocks. 



Dark red quartzitic rocks are found in several places, along with 

 the green schists. 



The green quartzitic rocks often exhibit sharp little folds marked 

 by thin mineral bands, which may indicate the original bedding- 

 planes. A strong southerly dip, due to foliation, predominates over 

 the whole of the Upper Tarnthal between the Sonnenspitz and 

 Eockner ridges. 



The Nederer section terminates with the quartzitic schists. No 

 actual occurrence of serpentine has as yet been observed on this 

 ridge, but the relation of the serpentine to the schists is well shown 

 in the neighbouring Upper Tarnthal and on the Eockner ridge. 



Between the altered schists and the serpentine are seen some 

 remarkable forms of ' ophicalcite.' Masses of calcareous schist, 

 several feet in thickness, have been injected along the foliation- 

 planes with the basic magma now represented by serpentine. Thin 

 bands and lenticles of serpentine alternating with the schist impart 

 to the rock a parallel structure, which gives the appearance of true 

 bedding and suggests a relation of conformity with the schists 

 below. These are, no doubt, some of the occurrences that led 

 Pichler to include ophicalcite and serpentine in a conformable 

 succession of sedimentary rocks. 



But at Matrei and Pfons, where the rock-series resembles that of 

 the Tarnthal, the ophicalcite is not in a form such as to suggest 

 the explanation here given of its origin. The parallel structure is 

 absent or imperfectly developed, and the calcite often appears in 

 veins. The mode of formation of these mixtures of serpentine and 

 calcareous rock is evidently subject to variation. 



The general dip of the schists under the serpentine-mass of the 

 Eockner led Prof. Eothpletz to the conclusion that the serpentine 

 was in the form of a sill resting upon the syncline of schists. But 

 the intrusive masses are very irregular in shape. This is well seen 

 in the case of the small serpentine-mass in the Upper Tarnthal, 

 on the southern slope of the Sonnenspitz ridge. 



In view of the more recent hypotheses of Alpine structure, which 

 assume a translation from a distance of some or all of the rocks 

 composing this mass, it seems important to distinguish between 

 characters impressed on the rocks in their original site (here called 

 oecogenous characters) and those which may have been acquired 

 during the movement (apcecous characters). 



Superimposed or Apoecous Characters of Rocks 

 of the Middle Zone. 



The distortion and partial foliation of the bedded limestones just 

 above the dolomite may have been imposed during a movement of 



