.74 SIERRA DE UMANGO 
rocks of the crystalline ba- - 
sement. Among the crystal- 
line hills in the latter part 
there are many small rem- 
nants of sandstones too. 
The hills are separated from 
the Cerro Villa Union com- 
plex by a train of piedmont 
gravels, running north-south 
(fig. 9). 
This broken ground may, 
as stated above, be regar- 
ded as a border tectonic to 
the great sunk area of the 
The dark slopes 
G 
| 
i 
fl 
i 
| 
| 
| 
| 
| 
| 
| 
the hills of Las Ramaditas. 
occupying the whole underground under the gravel sheet. The unsigned _ 
wana, principally pale yeliowish sandstone. 
3 Ne? Bu a Yang ta u ESR 
ee ea “ RR or past Br a Gen a a ARD 5 
\ 
I 
lj 
Il 
i 
ull 
| 
| 
ee ee eee 
pi Vinchina valley — Pagancillo 
lowland. The strata in the 
Cerro Punta Colorada dip © 
toward the lowland, except 
with many small irregula- 
tities. The northern part 
forms a kind of mantle above 
the core of the crystalline 
ground of Las Ramaditas. 
The sediments of this 
area are well exposed in 
many profiles, especially to 
the south of Las Ramaditas. | 
They were examined repea- | 
tedly by Bodenbender ; 
(1896, 1897, 1911), princ- & 
pally at the foot of the 
Cerro Punta Colorada. 
The series here is more 
The dotted parts (Gs) are red triassic beds, 
strata to the right (Gi) are of the lower Gond 
Fig. 9. Looking south over the gravel plain between the eastern side of the Cerro Villa Union and 
consist of old crystalline rocks, 
