Reconstruction of the environmental conditions for the past 2,000 years in the Perico River basin (NW Argentina) based on fossil pollen records

TORRES, GONZALO; LUPO, LILIANA; PÉREZ, CLAUDIO

VEGETATION HISTORY AND ARCHAEOBOTANY

SPRINGER

Lugar: Berlin; Año: 2022

0939-6314

In this paper we aim to reconstruct seasonal humid conditions of the past 2,000 years based on fossil pollen records fromhigh altitude sites (> 3,000 m a.s.l.) in NW Argentina. Palaeoenvironmental studies were conducted in two wetlands locatedin the upper basin of the Perico River (Jujuy province, Argentina). To assess the seasonal characteristics for different climaticperiods, we used the pollen index log10P/A to describe summer conditions, where P/A stands for the ratio betweenthe percentages of Poaceae (P) and Asteraceae (A). To interpret winter conditions we used log10T/A index. T/A is the ratiobetween the sum of percentages of transported pollen coming from Andean forest (T) and the percentage of Asteraceae (A).The prevalence of Poaceae pollen during certain time periods provides indirect information about soil moisture indicatingrainy summers related to an intensified activity of the South American Monsoon System (SAMS). In contrast, periods withpredominance of Asteraceae pollen suggest drier summers as a consequence of a reduction in SAMS activity. Structuralchanges from grassland to mixed steppe occurred at a multi-centennial scale, mainly driven by rainfall variability. The analysisof the log10T/A index enabled us to reconstruct the frequency of the mountain-valley breeze and indirectly to infer thewinter precipitation. Periods with a high input of tree pollen (> 20%) indicate high breeze frequency and consequently lesswinter precipitation and vice versa. We applied this reconstruction approach to characterize the seasonal humidity conditionsduring the Medieval Climate Anomaly, Little Ice Age and Current Warm Period in the study region.