UNDERSTANDING THE HYDROLOGICAL SYSTEM IN THE SOMÚN CURÁ PLATEAU, RIO NEGRO AND CHUBUT PROVINCES. ARGENTINA

PARICA, CLAUDIO A.; DAPEÑA, CRISTINA; REMESAL, MARCELA B.; BELLINO, LUCILA

Heidelberg

Otro; 24th Colloquium on Latin American Earth Sciences.; 2017

Heidelberg Center for the Environment, Universidad de Heidelberg

The Somún Curá Plateau extends for 25.000 km2 at South centre of Río Negro Provinceand North centre of Chubut Province in Argentine Patagonia. The entire region under studybelongs to a desert regime under extreme temperatures, -25°C in winter time to 45°C inSummer time, with averages between 3°C to 35°C with very dry conditions. The rainy seasonis spring time with 50 mm to 225 mm/year. The evaporation/transpiration is higher thanrains during all the year (Román and Sisul, 1984).The oldest rocks are precambrian, Mina Gonzalito Complex (schists and gneisses), lowerto middle Paleozoic magmatism is represented by acid intrusions and volcanics. Jurassictimes exhibit volcanic acid phenomena (Marifil Group). The Cretaceous is characterized bynon marine sediments of two different groups, Chubut and Neuquén (it depends of the describedarea). On lower tertiary times, marine sediments are described in the SarmientoGroup and Roca Fm. The upper Tertiary is represented by the Somún Curá Magmatic Province,in two stages; one belongs to the plateau stage, with basaltic rocks (Oligocene) andthe post plateau stage, represented by emissions of different rock types and compositions(basalts to trachytes). (Franchi et al., 2001). There are structures in a radial system, concentricsystem, both vertical and weak planes between different basaltic flows, horizontal tosub horizontal.Surface water is driven through streams, the most important are Valcheta (Rio Negro Province)and Telsen (Chubut Province). Into the basaltic plateau water circulation has placethrough the structures, from the upper levels by snow melting to lower levels, where thewater get salts and temperatures (23° C for southern water outlets and 45°C for northernwater outlets) (Parica et al., 2012). Isotopically the water can be divided in four differentgroups, one for the north, one for the south with an Atlantic origin of precipitations and twosmall groups with a local signature. The chemistry of water let to classify them into CalciumChloride, Calcium Sulfate and Calcium Bicarbonate, with light salinization index