Caracterización Isotópica del Acuifero Guarani Aflorante en el Norte de Uruguay.

COLLAZO, MARIA PAULA; DAPEÑA, CRISTINA; AUGE, MIGUEL; MONTAÑO, JORGE

Taller de Acuíferos Transfronterizos

Impresos S. A.

Lugar: Santa Fe; Año: 2007; p. 43 - 50

The outcrop area of the Guaraní Aquifer (AG) is located in northern and northern-central Uruguay, including parts of the Rivera and Tacuarembó departments. The outcropping GuaraniAquifer (AGa), ismade up of two units. The upper unit is restricted to the North and contained in the Rivera Formation is named Rivera Unit (UR). The lower unit is contained in the Tacuarembó Formation and occurs throughout all the studied area, and is named Tacuarembó Unit (UT). The Rivera Unit is made up of fine to medium reddish a eolian sandstone. It covers only the 15 % of the AGa, its thickness being in average 65 m and reaching maximumvalues of 100 mat high topographic levels (250 to 300 masl). The Tacuarembó Unit is made up of fine to very fine sandstones, with clayey siltstone intercalations, of pale and pink colours. Average thickness of this unit is 100m. It represents a hydrogeological unit of regional extension, of free to semiconfined behaviour. The isotopic composition (d2H, d18O) of the total groundwater shows similar values to the averages measured in the stations of the GNIP, indicating their meteoric origin. The values average d18O and d2H for the Unit Tacuarembó are respectively -5,6‰ and -31,5‰ and for the Unit Rivera are -5,4‰ and -30,4‰. The contents of 3H of the aquifer Rivera groundwater indicate smaller times of traffic and they are located in the watershed divisor.