8 SIERRA DE UMANGO 
A second expedition of Stelzner, realized during the following 
summer, was directed to regions more to the south, into the pro- 
vince of San Juan. During this journey Stelzner’s object of study | 
was principally the continental, clastic formations, reposing with creat | 
unconformity on the metamorphic schists. He discovered a rhaetic | 
flora, since closer examined by Geinitz (1876). 
The next geologist, who visited these regions, was Dr L. Bracke- 3 
busch, formerly professor of geology at Cordoba too. During extensive © 
and audacious journeys, this infatigable explorer twice crossed the ° 
region of the Sierra de Umango. In his „Mapa geolögico del inte- 
rior de la Republica Argentina“ + he has fixed, according to his and 
Stelzners observations, the main geological contours of these regi- 
ons. Brackebusch divided the formations here as follows: 1) ar- 
chaean, 2) rhaetic, 3) tertiary and quaternary. The whole material © 
collected by Brackebusch was then handed over to various spe- 
cialists in Germany, where also all the results were published. As x 
these laboratory-investigations generally were carried out without any : 
geological basis, their value is only a descriptive mineralogical one _ 
(resp. palaeontological). It is a pity, that Brackebusch never got 
any occasion to publish all his own extensive impressions except what 
„Mapa geolögico del interior de la Repüblica Argentina“ contains. 
During the later years Dr W. Bodenbender, at present professor of 
geology at Cördoba, has carried out a more systematic regional 
investigation in the western provinces, partly in the subandean region 
of La Rioja (1911). The Sierra de Umango area was, however, visited by 
him only to a small extent, principally along the borders of the Cerro 
Villa Union. But his exploration of the southern part of the province 
of La Rioja and also his monographical treatment of the Nevado 
de Famatina (1916), Sierra de Umango’s neighbour to the E, has offered 
much of comparative material to the study of the Sierra de Umango- 
geology. 
1 Scale 1: 1,000,000. Gotha 1891. 
