DETRITIC FORMATIONS 93 
Pen ck (1915) has really discovered similar beds (see later on). 
4 The occurrence of the brown sandstone only in the intermontane 
| zone may be explained in the following way: At the time when 
the zone in question was downfolded or downpressed (in miocene 
time?), the continental series in the area was much more complete 
than now. The late tertiary erosion had not yet to any greater 
extent worn away the upper members of the series. The brown 
Strata extended still ower greater; areas. After these movements 
| the late tertiary erosion destroyed all the brown layers, except 
where they lie safe in the longitudinal throws. 
It is impossible to express any opinion! about the age of the 
brown beds. The observation may be stated, that in the profile bet- 
ween Vinchina and Jaguel they change upward gradually into pale 
"brown sandstone like the rhaetic one in the Paso de Lamar, and 
that this later passes upward into softer, pale salmon and yel- 
lowish red sandy and conglomeratic beds of probably lower ter- 
tiary age. The brown layers expose at their base a substratum of 
red sandstone. Also on the southern slope of the Cerro Cordobés 
the brown layers show downward red and upward pale brown 
sandstones in conformity. _ 
Surely rhaetic strata do occur in the Cerro Rajado at the western 
entrance to the Paso de Lamar, being here a northern continuation 
of the extensive occurrences in the Sierra del Valle Fertil, disco- 
vered already by Stelzner-Geinitz [Bodenbender (1911)]. 
These strata contain remains of Thinnfeldia. The rhaetic forma- 
tion outcropping in the Paso de Lamar continues northward along 
the eastern side of the Cerro Bola. A farther extension of the rhae- 
4 the west of the valley of Fiambala, province of Catamarca, 
= 
1 Penck (1915) mentions the occurrence of dark brown and redbrown sand- 
stone series in the western Catamarca mountains, resting with unconformity (quasi 
conformity) over the „Paganzo“ sandstones. Because they carry andesitic tuffs and 
conglomerates, Penck regards their age as tertiary — that of the lower horizons 
as probably cretaceous. Judging from the lithological habit of the brown beds in 
the Umango area, a tertiary age seems there to be quite low. 
