Stable isotope hydrology in fractured and detritic aquifers at both sides of the South Atlantic Ocean: Mar del Plata (Argentina) and the Rawsonville and Sandspruit river catchment areas (South Africa)

GLOK GALLI, M.; DAMONS M.; SIWAWA S.; BOCANEGRA, E.M.; NEL J.; MAZVIMAVI D.; MARTINEZ D.E.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 73 p. 119 - 129

0895-9811

The aim of this study was to characterize stable isotopes of water in order to establish the relationship between fractured and detritic aquifers in similar hydrological environments located at both sides of the Atlantic Ocean: the Mar del Plata zone, placed in the Argentine Buenos Aires province in South America; and the Rawsonville and Sandspruit river catchment areas, situated in the Western Cape province, South Africa. For the Argentina study area, 30 rain water samples, and 18 and 131 groundwater samples from the fractured and detritic aquifers, respectively, were analyzed. In the case of the South African side, 26 precipitation samples and 30 groundwater samples from the fractured aquifer of the Rawsonville area; and 107 and 28 groundwater samples from the fractured and detritic aquifers of the Sandspruit catchment, respectively, were taken into account. Isotopic determinations were made through laser spectroscopy using a DLT-100 Liquid-Water Isotope Analyzer. For the Mar del Plata area, the more enriched δ2H and δ18O contents obtained in the detritic aquifer may be due to the occurrence of an evaporation process in its non-saturated zone as a consequence of the existence of very low topographic gradients and fine grained sediments. This phenomenon is not evident in the Sandspruit river catchment site?s detritic aquifer, because its sandy lithological composition allows a faster infiltration rate than in the loess which compounds the Pampeano aquifer in Argentina. Particularly for the Rawsonville area?s fractured aquifer, the stable isotope composition of the samples indicates that this aquifer recharge has occurred at higher altitude or during winter months, and also demonstrates the possibility of groundwater mixing or a surface water infiltration causing some indirect recharge.