60 SIERRA DE UMANGO | 4 
there are many such younger zones of true sedimentary origin. + 
Keidel? and Rassmuss? have later on also expressed the opinion, 
that they may represent in some parts lower palaeozoic members, and 
that thence the hiatus under the covering permo-carboniferous strata 
may be less important than corresponding to the old opinion of 
Stelzner. | 
It is, of course, in many cases very difficult to determine, if the 
downfolded younger members really are of lower palaeozoic age. — 
From the province of Catamarca Rassmuss has reported a complex k 
of probable algonkian, separated from an older archaean body by a | 
marked unconformity (basal conglomerate). The younger complex i 
consists of quartzites and mica schists. In the sierras to the west 4 
from Tucumän and further to the north there is a broad zone of 
chloritic and other schists, extending in the general N—S direction. 
The schists are of precambrian age, as shown by Keidel? from 
his investigations farther to the north, in the province of Salta, — 
where fossiliferous upper cambrian with a marked unconformity | 
lies over the strongly folded (and also mylonitized) complex of the : 
northern continuation of the same schists. ; 
Apart from these sedimentary zones the bulk of the complex of 
the „Sierras pampeanas“ seems to consist of gneissic and mingled © 
rocks together with extensive granitic bodies. The last named are ; 
partly of palaeozoic age, as shown by the fact, that they penetrate © 
the sedimentary rock members (limestones a. o.), whose lower pa- | 
laeozoic age is beyound doubt. Great gneissic complexes are met 
with in the Sierra de Cördoba, Sierra de San Luis and also in the ~ 
Sierra de Velazco. 
The coincidence of the orientation of all the schistose and gneissic | 
rocks of the „Sierras pampeanas“ (incl. the Famatina—Umango 
1G. Bodenbender (1911). See the geological map. 
2H. Keidel (1914). Page 674. 
3 Juan Rassmuss (1916). 
4H. Keidel (1914). Page 674. 
