UR nun Zum m ee na 
GEOMORPHOLOGY 117 
tains of the Catamarca province (in the north) southward with an- 
increasing breadth and ending in the Pagancillo lowland. The bot- 
tom of this great valley consists of sandstones of the continental 
series, mostly of red colours, to the south, however, overlaid with 
younger, tertiary strata, attaining a great extension in the Pagan- 
- cillo lowland. It is evident that these substrata of sandstones ge- 
_nerally must be of no great thickness, because in the middle part of 
the valley, in the vicinity of Villa Castelli, a great number of smaller 
crystalline hills occurs, covering quite a considerable area (Cerro 
_ Asperecito, etc.) The walls of the valley almost expose the crystal- 
line ground. North from the Sierra de Umango ridge the western 
wall is, however, a sandstone ridge, separating the valley from the 
Jaguel bolson. More to the south the same side is formed by the 
sandstone hills of the Cerro Punta Colorada. The eastern wall, the high 
slope of the Famatina mountain, shows in the foreground a series 
of smaller crystalline hills extending from Villa Castelli some lea- 
gues to the south. 
The tectonical type of the valley is a longitudinal throw or „graben“. 
- There; have been minor faults along the chief lines of dislocation, 
as is seen from the occurrence of several smaller faultblocks of 
longitudinal extension, now appearing as foothills. The strata of the 
Cerro Punta Colorada are tilted in direction of the valley and show a 
continuation into the bottom layers. The Cerro Punta Colorada is 
thence formed by a bending up of the substrata of the valley by the rising 
of the basement here in the form of a separated fault block. Or 
more exactly, here is a whole system of small blocks, as stated 
before. 
The Pagancillo lowland. 
The lowland forms an immediate continuation of the Vinchina 
valley. It is limited to the east by a southern prolongation of the 
great western flanc-fault of the Famatina mts, here cutting across an 
uplifted table of the continental sandstones and forming a bluff or 
