Vegetation dynamics from Lago San Martín area (Southwest Patagonia, Argentina) during the last 6500 cal B.P.

BAMONTE, FP, MV MANCINI , GD SOTTILE, MA MARCOS, C GOGORZA; C. GOGORZA

VEGETATION HISTORY AND ARCHAEOBOTANY

SPRINGER

Lugar: Berlin; Año: 2015 vol. 24 p. 267 - 277

0939-6314

We report a palaeoenvironmental reconstruction since 6,650 cal. BP from the Lago San Martín area, from a peat-bog sequence, Mallín Paisano Desconocido, located at 48° 58? S; 72° 14? W. Between 6650 and 4500 cal B.P. we can infer a shrub steppe dominated by Asteraceae subf. Asteroideae associated with other shrubs under relatively dry conditions, through an intensification of the westerly wind belt and a steepening in the west-east precipitation gradient. From 4500 to 3000 cal B.P. a shrub-grass steppe development suggests a slight increase in moisture conditions although the environmental conditions remain dry. Form 3000 cal BP a grass steppe represented by Poaceae and subordinated herbs 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 to the beginning of the Little Ice Age, whereas the last century shows signals of anthropic impact The palaeoenvironmental interpretation from Lago San Martín basin is based in moisture availability variations in relation with precipitation patterns changes of westerly origin. These trends are consistent with interpretations of records 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 within a regional framework interpreting them in relation to southern past climatic changes. At a regional scale the records show an increase in westerly intensity during the mid- Holocene, whereas weaker westerly flows are postulated for the late Holocene.