High-altitude limnogeology at the Eastern Cordillera (Central Andes, northwestern Argentina): evidences of late Quaternary climate changes.

GUERRA, LUCIA; MATEO MARTINI; PIOVANO, EDUARDO; ARIZTEGUI, DANIEL

Viena

Congreso; European Geoscience Union General (EGU) Assembly 2018; 2018

The region of Eastern Cordillera located above the 4000 m a.s.l. in the Central Andes from northwestern Argentina,is characterized by extreme climatic conditions with low precipitation (< 400 mm yr-1), and wide temperature amplitudes.In this high-altitude region, the sedimentary records of lakes and wetlands constitute exceptional sourcesfor documenting the abrupt climate changes occurred during the late Quaternary. Multiproxy limnogeological studiesof two different lacustrine systems allow identifying major sedimentological changes and understanding theirrelationship to regional paleoclimate. Laguna Salada Grande (23S/65W) is a shallow tectonic lake located at4102 m a.s.l. at the Sierra de Aparzo. It is an endorheic basin that has not been glaciated during the late Quaternary.Paleoshorelines situated 20 m above the present lake level suggest the occurrence of a deeper paleolake.Sedimentary cores (1.5 m length) and gully outcrops display massive and finely laminated units. Geomorphologicalfeatures combined with lacustrine core stratigraphy allow linking the main paleoshorelines with those changesobserved in the sedimentary record. Laguna Leoneajo (22S/65W) is a small wetland and exorheic basin. It islocated in a glacial valley at 4526 m a.s.l., downstream of an active rock glacier, at the Sierra de Santa Victoria.Sedimentary cores (1.5 m length) reaching the lake basement encompass the environmental history since the lastdeglaciation. Here, we present the first results of multiple analyses on samples from cores and outcrops includingpetrophysical properties (magnetic susceptibility and grain size measurements), nitrogen, organic matter and carbonatecontents, microstratigraphy, and detailed mineralogy along with a radiocarbon chronology. These resultscombined with different paleoclimatological records in the region (e.g. glacial deposits, lake transgressions) willprovide critical information to better understand past patterns of atmospheric circulation in the Central Andeanregion, where the knowledge about past climate conditions is still limited.