Fossil pollen records indicate that Patagonian desertification was not solely a consequence of Andean uplift

PALAZZESI, LUIS; BARREDA, VIVIANA; CUITIÑO, JOSÉ IGNACIO; GULER, M. VERÓNICA; TELLERIA, M.C.; VENTURA SANTOS, ROBERTO

NATURE COMMUNICATIONS

Macmillan Publishers Limited

Año: 2014 vol. 5 p. 1 - 8

2041-1723

The Patagonian steppe -a massive rain-shadow on the lee side of the southern Andes- is assumed to have existed ~15-12 Myr as a consequence of the southern Andean uplift. However, fossil evidence supporting this assumption is limited. Here we quantitatively estimate climatic conditions and plant richness for the interval ~10-6 Myr based on the study and bioclimatic analysis of terrestrially derived spore-pollen assemblages preserved in well-constrained Patagonian marine deposits . Our analyses indicate a mesothermal climate, with mean temperatures of the coldest quarter between 11.4 {degree sign}C and 16.9 {degree sign}C (current: ~3.5{degree sign}C) and annual precipitation rarely below 661 mm (current: ~200 mm). Rarefied richness reveals a significantly more diverse flora during the late Miocene than today at the same latitude but comparable with that approximately 2000 km further northeast at mid-latitudes in the Brazilian coast. We infer that the Patagonian desertification was not solely a consequence of the Andean-uplift as previously insinuated.