36 SIERRA DE UMANGO 
to the immediate vicinity of the batholith, so that they may more 
conveniently be treated apart from all the other metamorphic rocks, — 
occurring in the Sierra de Umango area. 
The foothills of the Nevado are rugged, completely barren ridges - 
of more longitudinal extension. They rise abruptly over the exten- 
sive mountain gravel plains and are separated from the granitic 
slope of the Nevado by similar gravels. The best exposures are 
to be found opposite the village of Villa Castelli, in the Cerro La 
Vatea (Batea) (not visible on the map, fig. 5). 
The Famatina granite has in this locality penetrated into and 
dissolved a complex principally of mica schist and amphibolite. 
In accordance with the general northerly orientation of the Umango 
schists the inclusions of the Nevado foothills show the same strike, 
in spite of the intense mingling with granitic material. Irregula- 
rities have been developed more in details. 
The manner of intrusion depends on the lithological character of 
the penetrated rocks. The mica schist has generally been intensely 
exfoliated along the schistosity-jointing-planes and verbally penetrated 
with granitic „blood“. This process was accompanied by an intri- 
cate folding on a small scale indicating a plastic stage of the rock 
mixture, a contortion without fractures. This phenomenon has been 
called by Sederholm! ,ptygmatic folding“, a very characte- 
ristic feature in the deeper archaean terrane in Finland and else- 
where. 
The amphibolite has mostly been shattered into great eruptive 
breccias with a matrix, composed of acid differentiations from the 
granitic magma, a very common phenomenon in every such case 
of injection. ? 
1 J. J. Sederholm: Ueber ptygmatische Faltungen. Neues Jahrbuch für Mi- 
neralogie, etc. Beil. Bd. 36. 2 Heft. Sept. 1913. Page 491. 
2 Adams and Barlow: The Geology of the Haliburton and Bancroft Areas, 
Province of Ontario. Canada. Dept of Mines. Geol. Surv. Branch. Mem. 6. 1910. 
J. J. Sederholm: Om granit och gneis. Bull. Comm. Géol. de Finlande. N:o 
23. Helsingfors 1907. With an english summary. 
a 
a 
a 
a 
| 
H 
al 
oy 
bet 
| 
y 
Vi 
kv 
| 
he 
N 
a 
f 
( 
EIN N 
u = 
Pe aes ws 
EEE EN 
kn 
ee — 
rnit TIERE 
FREE res te EVEN 
Se Sete 
