Vegetation dynamics from Lago San Martín area (Southwest Patagonia, Argentina) during the last 6500 cal yrs BP

BAMONTE, FLORENCIA; MANCINI, M. V.; SOTTILE, GONZALO; MARCOS, ALEJANDRA; GOGORZA, C.

VEGETATION HISTORY AND ARCHAEOBOTANY

SPRINGER

Lugar: Berlin; Año: 2014

0939-6314

We report the palaeoenvironmental reconstruction from Lago San Martín area, from a peat-bogsequence, Mallín Paisano Desconocido, located at 48° 58? S; 72° 14? W since 6650 cal B.P. Between 6650 and 4500 cal B.P. we can infer a shrub steppe dominated by Asteraceae subf. Asteroideae associated to others shrubs under relatively dry conditions, by an intensification of the westerly wind belt and a steepening in the west-east precipitation gradient. From 4500 to 3000 cal yr B.P. a shrub-grass steppe development suggest a slight increase in moisture conditions although the environmental conditions remain dry. From 3000 cal B.P. the grass steppe represented by Poaceae and subordinated herbs was developed suggesting an increase in moisture availability and weaker westerly flow precipitation. The last 400 cal B.P. was characterized by a change from grass to shrubby communities which could be related tothe beginning of the Little Ice Age (LIA), whereas the last century shows signals of anthropic impact. The palaeoenvironmental interpretation from Lago San Martín basin is based on moisture availability variations in relation with precipitation patterns changes of westerly origin. These trends are consistent with record interpretations from the Andean and extra-Andean areas. The comparison with other sequences allows us to interpret the palaeoenvironmental changes in the Lago San Martín area and to integrate these variations to a regional framework and interpret them in relation with southern climatic past changes. At regional scale, the records show an increase in westerly intensity during the mid Holocene, whereas weaker westerly flow were postulated for the late Holocene.