Tephrochronological data from Lanin National Park: Towards a reconstruction of the Holocene volcanic history of Northern Patagonia, Argentina

VALERIA OUTES; CAROLINA MANZONI; GUSTAVO VILLAROSA; IVAN PETRINOVIC; JULIETA COTTET; CATLINA BALBIS

PUERTO VARAS

Congreso; CITIES ON VOLCANOES 9; 2016

SERNAGEOMIN-IAVCEI

We present the first findings that make thereconstruction of the Holocene volcanic history for the Lanín system possible,as well as a first estimate of the territorial extent of the impact ofexplosive eruptions in the Lanín National Park area, by identifying theresulting tephra deposits and corresponding eruptive center. Three minorvolcanic centers (La Angostura and Arenal cones, and the Achen Ñiyeu volcanowith its associated lava flow), together with Lanín and Quetrupillánstratovolcanoes, are the main active volcanoes with Holocene explosive activityin the area, corresponding to the Villarica-Lanín volcanic system.  Short cores from Huaca Mamuil (HM) andHuechulafquen lakes together with road-cuts and exposures north and south ofLanín volcano were studied and AMS dated. Twelve ashfall deposits wereidentified and characterized. A flow deposit overlain by a tephra fall layerexposed in several road-cuts in Curruhue area, was dated at 9560-10520 cal yrB.P. El Escorial lava flow, originated in the Achen Ñiyeu cone, was dated witha maximum age at 1260-1060 cal yr B.P. A dacitic tephra identified in HM coresis attributed to the Quetrupillan volcano last major eruption (ca. 1650 yrB.P.) and is used as chronostratigraphical marker. Several other tephra layersare attributed to La Angostura cone according to their petrographiccharacteristics. The youngest tephra identified in the cores corresponds to the2015 Calbuco eruption. Further work is being carried out to complete thisreconstruction in order to improve volcanic hazard assessments for thisemblematic region.