Palynological evidence of the geoecological belts dynamics from Eastern Cordillera of NW Argentina (23° S) during the Pre-Last Glacial Maximum

Gonzalo R Torres,Liliana C Lupo,Julio J Kulemeyer,Claudio F Pérez

doi:10.5027/andgeov43n2-a01

Abstract

This paper presents the first palynological record for the dynamics of geoecological belts of the Eastern Cordillera in northwestern Argentina prior to the Last Glacial Maximum (LGM). The study was carried out on a 5-m deep sedimentary core raised at Laguna Blanca (23°09’S, 65°12’W; 4,256 m a.s.l.), province of Jujuy. The geochronology was based on three 14C dating by AMS method. Results show the sensitive response of the geoecological belts to temperature and effective moisture variations from ca. 29,000 to ca. 25,000 cal. years BP. The High Andean belt probably suffered an altitudinal descent forced by intense cold climate conditions ca. 29,000 cal. years BP, and may have reached a comparable distribution to the present one on 26,300 cal. years BP, favored by a milder climate. The Puna belt did not suffer great changes, since it remained with low representation in the pollen spectrum. High percentages of tree species from the Yungas ca. 29,000 cal. years BP are probably a response to the intensification of anabatic winds ascending the slope of the Sub-Andean Range towards the Eastern Cordillera. These results represent an important contribution to the paleoenvironmental discussion of the Late Pleistocene for the northwestern Argentina, where the available information on vegetation history is scarce.

Highlights

The high mountain sectors of the Central Andes (16°-30° S) are key regions for studying the paleoenvironmental evolution during the Quaternary
This paper presents the first palynological record for the dynamics of geoecological belts of the Eastern Cordillera in northwestern Argentina prior to the Last Glacial Maximum (LGM)
In the Bolivian Altiplano, the Late Pleistocene climate reconstructions has been discussed in several studies which suggest that the transition to the Last Glacial Maximum (LGM, 26,000-21,000 cal. years BP /22,000-18,000 years BP) was a cold and wet period with regional variations of moisture availability

Summary

Introduction

The high mountain sectors of the Central Andes (16°-30° S) are key regions for studying the paleoenvironmental evolution during the Quaternary Their sensitivity to subtle effective moisture (precipitation minus evaporation) and temperature variations cause changes inducing vertical migration of vegetation associations along the slopes (Colinvaux et al, 1997; Grosjean et al, 2001; Paduano et al, 2003; Gosling et al, 2008). Mean precipitations 30% higher (Blodgett et al, 1997) and temperatures 5 and 8 °C less than present values were suggested (Thompson et al, 1998; Argollo and Mourguiart, 2000; Imhof et al, 2006) During this cooling period, lake and paleolake responses in the main Altiplano basin have been reconstructed. Lake Titicaca water level increased under the prevalence of cold conditions and the Puna Brava vegetation descended ca. 21,500 cal. years BP (Baker et al, 2001; Paduano et al, 2003; Tapia et al, 2003) while in the Uyuni salt lake the Sajsi cycle (between 24,000 and 20,500 cal. years BP) was contemporary to the LGM (Placzek et al, 2006; Blard et al, 2011)

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Conclusion