A) THE ”PREGRANITIC” SUPERCRUSTAL ROCKS 
OF THE SIERRA DE UMANGO AREA. 
a) THE SEDIMENTARY SCHISTS. 
Engaged in a careful study of the lithological composition of 
the Sierra de Umango crystalline basement, one must arrive at the 
conclusion, that there is a great bulk of sedimentary and effusive 
members, — a „pregranitic“ unity, while granites older than the 
postsilurian(?) Famatina granite, do not occur there. The sedimen- 
tary part of this bulk consists principally of three distinct lithological 
groups: limestones, quartzitic schists and argillaceous schists. 
The relative quantities of these components are very difficult to 
estimate, because the original succession is lost by various proces- 
ses of disturbances, causing faults, folds, charriages (overthrusts), 
etc. with accompanying thickening and inversion of the strata. The 
limestone-amphibolite banks with their fantastic torsion pheno- 
mena offer an evident proof of the high grade of disturbances, 
suffered by the basement in question (see the fig. 3). 
A conspicuous circumstance is the great thickness of the limestone 
banks especially in the western part of the region, where the lime- 
stone alone forms whole ridges and hills, the total thickness of the 
ayers attaining some hundred meters without any tectonical thicke- 
ning. This abundance of limestone stands in a marked contrast to 
the experiences in the Famatina mountain, where such layers are 
thin and scarce!. Also in the other pampean sierras we find 
1 See: G. Bodenbender (1916). 
