94 SIERRA DE UMANGO 
tic strata in the Umango area seems to be doubtful; perhaps the 
pale-coloured members of the ,intermontane zone" are ofthe same age. 
The many rhaetic occurrences indicated on the map by Bracke- 
busch (1891) from the Umango area are, as stated above, incor- 
rect.’ ö 
Over the rhaetic beds in the Paso de Lamar follows concordantly ; 
the upper red sandstone perhaps of jurassic — cretaceous age, very 
similar to the triassic one [Bodenb!ender (1911)]. The great litho- 
logical similarity with the triassic sandstones makes it very difficult | 
to judge about the age, especially regarding the small isolated ; 
remnants of such red sandstone, downfaulted into the crystalline ba- | 
sement. If the ,cretaceous* occurrences indicated by Bodenben- 
der (1911) from the eastern parts of the Cerro Villa Union are 
in reality all of this age, seems doubtful. For instance, the floor 
of the valley bottom in the vicinity of the Villa Union forms the 
direct continuation of the upbent strata at the eastern slope of 
the Cerro Punta Colorada and nevertheless the former are indica- 
ted as „cretaceous“, the latter as „Paganzo“. | 
Still younger strata, belonging to the miocene, etc. Calchaqui-beds 
(„estratos calchaquefios‘, named after great occurrences in the valley 
of Calchaqui in the province of Tucumän) have developed on quite 
a considerable scale in the Umango area, where they occupy pro- 
bably the greater part of the Pagancillo lowland. They also do occur 
in the tectonical depression of Zapallar to the west, so in the Ja- 
guel depression too, where they lie conformably over the older 
continental sandstones (profile Vinchina—Jaguel). The Calchaqui- 
strata consist of a series of soft, pale yellowish, pale salmon-red and 
white nuancering sandstone-marls and conglomerates. 
A coarse gray conglomerate indicating a sudden change in the 
conditions of sedimentation does cover with a marked overlapping ~ 
unconformity these strata. This conglomerate is, however, of a small 
extension. All its pebbles consist of old crystalline rocks. 
The probable stratigraphical subdivisions of the pre- 
