Isotopic composition and origin of the precipitation in Northern Chile

A 3 a data set of isotopes in precipitation from northern Chile show a very distinct pattern, with δ18O values ranging between −18 and −15‰ at high altitude stations, compared to δ18O values between −10 and −6‰ at the lower altitude areas. The 18O-depleted values observed in the high altitude area, the Altiplano, are related to processes that affect the air masses that originated over the Atlantic, cross the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated with air masses from the Pacific, may contribute to the 18O-enriched values observed in the lower altitude areas. Similar isotopic patterns are documented in springs and groundwater indicating that the data presented in this paper are an accurate representation of the long term behavior isotopic composition of rain in northern Chile.