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u: DETRITIC FORMATIONS 67 
varying height of an once covering mantle, uplifted by the horst- 
movement. These fringes are only the visible edges of the vast 
sunken parts of the same formations, occupying the space between 
the Sierras and today completely covered with the more recent 
pampa accumulations. Nearer to the Andes the outcrops of the 
mantle are growing larger, because the tectonical throws are getting 
narrower and the pampean accumulations are decreasing in thick- 
ness in the same direction. Here the mantle-outcrops also climb to 
greater heights over the valley floors. Especially in the provinces 
of La Rioja and Catamarca these continental series are developed 
to great extent in the geological structure. Their most typical re- 
presentatives one will find in the former province incl. the Sierra 
’ de Umango area, and therefore they have been named the La Rioja 
strata. They correspond to the „Paganzo“ of Bodenbender.! 
Farther to the south in the Precordilleran zone the extension of 
the continental strata, according to the geological map by Stap- 
penbeck (1910) comprising the area from Mendoza to Jachal, is 
less conspicuous, but still quite considerable. 
The principal extension of the „Paganzo“ or La Rioja strata was 
studied and fixed on the map already 40 years ago by Ludw. 
Brackebusch.? The series in question was called by him „ferre- 
nos reticos", according to the earlier determinations by Geinitz 
(1876). They include also many volcanic sheets. The „rhaetic“ 
age, however, was in many cases considered by Brackebusch 
as doubtful, as may be seen from. the many notes of interrogation 
on the map. Later on Bodenbender (1896) divided the series 
more closely into „carboniferous“, „permian“, „triassic* and „rhae- 
tic" formations. This division was partly based on discoveries of 
plant remains in the strata. In a later paper by the same author 
(1911) one find the following scheme: the carboniferous, permian 
1 (1904). See later on. 
2 Ludw. Brackebusch, I. c. (1891). 
