18 | SIERRA DE UMANGO 
bearing too and very intensely microfolded. The occurrence of this | 
type is quite limited, appearing, as mentioned, only in alternance — 
with quartzitic schists. Microscopically the sericitic schist shows a 
considerable amount of ferri-oxyde, forming parallel thin zones and q 
very markedly indicating the microfold-structure (see Plate I, fig. 2). 4 
The mica schists are also to be found in various parts of the 
Umango area as small intercalations between other thin layers in 
the so called banded rocks, below more closely characterized. The 4 
highly granitized areas, as the summit of the Cerro Cacho and in — 
the eastern part of the region, are also represented by mica schists. a 
The mingled product, called by Sederholm migmatite, and also j 
wholly resorbed rocks, appear many times here, as e. g. in the q 
western foothills of the Nevado de Famatina. 4 
According to Bodenbender there are abundantly in the last 3 
named mountain in the higher regions, wholly surrounded by gra- q 
nite (ci. the little sketch map, page 30), micaschists with basic in- ~ 
trusive sheets of exactly the same appearance as in the Umango ~ 
area. They represent metamorphosed, cambrosilurian slates. The — 
writer had occasion to see these schists, as he crossed the moun- q 
tain on his return journey from the Umango district, and he could — 
prove their similar appearance. | 
Whereas in the Famatina area there are in some parts but slightly — 
metamorphosed facies of the slates and other sedimentary rocks - 
(the fossiliferous parts), all the sediments of pregranitic age in the ° 
Umango area have a very strong metamorphic habit to make it - 
hopeless to find any tracks of fossils or even to meet any possi- 1 
bility of studying the original lithological structures. The changes — 
have been not only of contactmetamorphic nature but also kata- 
clastic in many ways. 
If it is correct to consider the easternmost part of the Umango | 
complex, situated nearest to the Famatina granite batholith, as the a 
lowermost horizon, and the western parts generally as crustal masses 
of a higher position, one may state, with reference to the distribution 
