CRYSTALLINE BASEMENT ; 55 
ming the named zones as ways of weakness, the mica planes having 
_ played the part of gliding surfaces. 
On a very much smaller scale we find the pression phenomena 
i 
_ developed in the quartzitic schists, where generally every kind of 
_ crushing is lacking. Also the grains of quartz are individually well 
conserved (after the last recrystallization) and no signs of ,undu- 
lating extinction’ can be detected. The slight mechanical defor- 
ua 6 Ene ro 
_ mation can be seen already in handspecimen, whose surface shows 
a distinct glassy apparition (in the transverse cuts). This remarkable 
- consistense of the rock can be explained in general by a greater 
-hardness and coherence characterizing this kind of crystalline schists. 
The crystalline limestone, occurring, as mentioned, principally as 
folded banks in the western part of the Umango area, was intruded 
by white granite and pegmatite simultaneous with the folding process. 
By this process the rock became completely recrystallized, and 
afterward — during the tertiary time — no crushing deformations 
have occurred, except in some isolated localities, where faults cut 
across the banks. 
c) KATACLASIS IN SOME „DARK SCHISTS“. 
A group of dark schistose rocks, characterized above petrographi- 
cally, affords a very excellent example of the tertiary dynamic meta- 
morphism. They are sometimes of a doubtiul origin. Compared with 
the ordinary amphibolites they are much more granulated, a fact 
preventing essentially the examination of the real nature of the rocks. 
Microscopically the dark schists often develop a porphyroclastic 
structure (Plate VI, fig. 1). The larger grains are composed of 
plagioclase and amphibole. When quartz occurs, it has been so 
intensely granulated, that it forms a kind of groundmass. This fine 
detritic mass has a flow arrangement, bending around the larger 
grains and containing also abundant minute amphibole and biotite 
fragments of elongated forms, especially marking the flowage direc- 
tions. An interesting example is illustrated on plate VI, fig. 2, where 
