CRYSTALLINE BASEMENT 59 
phyry complex, composing the higher parts of the ridges. The por- 
 phyry series stands, as seems, in magmatic relation to the granite. 
At the western foot of the mountain lower „Paganzo“ (pale coloured 
“sandstones and conglomerates) lie on a granite ground, while on 
‘the eastern side similar beds are downfaulted between the old por- 
| phyries and vertically tilted mica schists, the latter forming moun- 
‘tains and ridges to the east from the Nevado. Nearer to Chilecito 
the granite again appears. 
It seems quite probable, that in time between the consolidation 
of the Famatina batholith and accompanying porphyries, and the 
sedimentation of the continental strata there took place a great 
break in the succession of the geological records, i. e. a hiatus of 
erosion. The basal plane of the ,Paganzo“ series represents without 
doubt in general a deep geological horizon (cut) indicated by the 
predominance in the basement of coarse grained granites, molten 
and resorbed inclusions of rocks and also by the steep position of 
the mica schists. The observed ,concordance* mentioned by Stelz- 
ner and Bodenbender as existing between these schists and the 
„Paganzo“ strata may probably be explained as tectonical juxta- 
position, a common phenomenon also in the region of the Sierra de 
-Umango. I am consequently inclined to accept the old opinion of 
Stelzner, regarding the Famatina granite being of postsilurian age. 
When regarding the other „Sierras pampeanas“ one may find, 
that there occur in many regions zones of sedimentary schists, 
limestones and conglomerates, apparently representing younger 
members, downfolded in the old precambrian gneisses and intruded 
schists. In the Sierra de Cordoba? for instance, we find amidst an 
old gneissic terrane a smaller remnant of coarse clastic layers, pres- 
sed conformably to the former and also many outcrops of folded 
limestone zones of evidently silurian habit. Also in the Sierra del 
Gigante, in the Sierra de los Llanos_and in the Sierra Pié de Palo 
' 1G. Bodenbender: La Sierra de Cordoba. Anales del Ministerio de Agri- 
cultura de la Naciön. Secciön Geologia, Tomo I. N:o 2. Buenos Aires 1905. 
