CONICET | Buscador de Institutos y Recursos Humanos

In southern South America the acquisition of high-quality Holocene paleoclimate data is a priority due to the paucity of complete, continuous and well-dated records. We report preliminary results from a combined sedimentological and palynological study of an alluvial fan sequence and laterally connected sedimentary deposits at Agua Buena, east of the Andes. The main geomorphological units of the area were identified and mapped based on satellite image analysis and multiple field surveys. The sedimentological and pollen results allowed us to reconstruct the development of some environments. The Agua Buena record corresponds to the distal facies of a large alluvial fan that has been active since ca. 4.1 ka. Organic-rich levels were formed during the development of wetlands ("vegas") dominated by Cyperaceae, Juncaceae and Poaceae. These highly productive environments with almost permanent water saturation were important between 4.1 and 2.8 cal ka BP, indicating relatively stable conditions. After 2.8 cal ka BP, the organic content was comparatively lower with increasing sedimentation rates that are indicative of higher fluvial discharges. This information is fundamental to interpret pollen and charcoal records in the area and to evaluate their representativeness and potential to reconstruct past local and regional vegetation.