Degradation and formation of Puna vegas (900-150 years BP), southern Puna (26 º S). Landscape response to climate or man?

Acta geológica 24 (1-2):2012

Abstract

In the southern Puna of Argentina there are evidences of recent physical degradation of wetlands called “vegas”. The question arises about the age and causes of degradation. Therefore, the purpose of this paper is to study the causes of degradation and whether these are associated with known palaeoclimatic events or human actions. The dating of four paleosoils in degraded vegas are distributed in two age groups: ca. 700-600 years BP and ca. 300-150 years BP. The results indicate soil degradation is found in all wetlands regardless of the archeological and geomorphic settings. Degradation is mainly located at the distal end of the vegas, where evapotranspiration is high- er. In addition, soil wetland erosion is greater in extent and intensity in broad vegas with small catchment areas (less than 25 km2) located above 4500 m.a.s.l. The study shows that the degradation of the vegas occurred at least three times in the last 1000 years and the last retreat occurred during historical time (less than 150 years BP). Degradation could be related to the decline and instability of the groundwater table due to an increase in aridity. The low-altitude (less than 4500 m.a.s.l.) and smaller area catchment basins would have been the most susceptible to degradation.