Mid- to Late Holocene Environmental Evolution of a High Mountain Wetland in the Subtropical Andes Cordillera of Argentina

Abstract

Wetlands in mountains are highly dynamic and provide ecosystem services to human wellbeing. Understanding temporal and spatial wetland dynamics is crucial for successful management. This paper presents the reconstruction of a mire evolution at a high-altitude Andean valley in central-western Argentina, in subtropical South America (30°-36° S), during the Mid- and Late Holocene. The research is based on sedimentological and pollen analysis from a sedimentary section of 3.2 m thick exposed at the El Peñón valley. The record begins with an outwash environment after ca. 5700 cal. yrs BP associated with Pteridophytes dominance, followed by the development of a mire environment after ca. 3700 cal. yrs BP associated with Cyperaceae dominance. The environmental and vegetation changes are hypothesised to have occurred in response to a shift from cold to warmer conditions. Colder environments may have occurred again between 800 until < 600 cal. yrs BP, probably associated with the Little Ice Age. Tephra inputs are evidenced in the record from 1200 years BP onwards. However, the results do not show any conclusive evidence about the impact of volcanism in the dynamics of the wetland. High Amaranthaceae proportions would evidence human activities in the high-altitude valleys of the southern Andes, probably for the last 250 cal. yrs BP. This work permitted us to infer the evolution of the El Peñón wetland under multiple concurrent forcing factors from the Mid- Holocene onwards at different temporal scales, i.e. climate during the last 5700 yrs, and volcanism and anthropogenic impacts during the last millennium.