Use of dendrochronological and radiocarbon methods for dating a volcanic event in the Lake District, northern Patagonian Andes

CASTELLER ALEJANDRO; STOFFEL MARKUS; CRESPO SEBASTIAN; ARBELLAY ESTELLE; VILLALBA RICARDO

Rovaniemi

Conferencia; WorldDendro 2010; 2010

Finnish Forest Research Institute (Metla) in conjunction with Association for Tree-Ring Research, Tree Ring Society, Asian Dendrochronology Association, and IUFRO WP 5.01.07 Tree Ring Analysis.

Volcanic activity is a common feature that modifies the landscape and eventually puts at risksettlements and roads in the Lake District of the Patagonian Andes. Although some volcanoesfrom this region are presently extinct, most have records of past activity during the Holocene,including eruptions in the past centuries. According to estimations from different sources, thevolcano ?Ayen Niyeu?, located in the Parque Nacional Lanín, Neuquén, Argentina (39°50'02"S,71°31'40"W) produced a large lava-flow event ca. 470 years BP. The large basaltic flow dammeda transversal valley to the water flow creating ?Lago Verde? lake. As a result, a large portion of aNothofagus dombeyii- dominated forest was flooded. In February 2009 we sampled 27 crosssectionsof N. dombeyii trees flooded by the volcanic event. The upper parts of these trees hadrecently been exposed due to drought conditions prevailing over the past few years in the region.In addition, 15 living N. dombeyii trees not flooded by the event were sampled at a near location,in order to attempt dating the floating tree-ring chronologies with this reference tree-ringchronology. Radiocarbon dating techniques are presently being conducted on pieces of sixflooded trees; the first dating indicates an age of 475±35 radiocarbon years BP.