Spatial variability of the modern radiocarbon reservoir effect in the high-altitude lake Laguna del Peinado (southern Puna Plateau, Argentina)

• Published in: Geochronology (Göttingen. Online) Vol. 5; no. 2; pp. 333 - 344
• Main Authors: Vignoni, Paula A., Córdoba, Francisco E., Tjallingii, Rik, Santamans, Carla, Lupo, Liliana C., Brauer, Achim
• Format: Journal Article
• Language: English
• Published: Göttingen Copernicus GmbH 08-08-2023; Copernicus Publications
• Subjects: Age; Altitude; Aquatic plants; Atmospheric models; Carbon 14; Carbon dioxide; Field study; Groundwater; High altitude; High-altitude environments; Hot springs; Lake basins; Lakes; Littoral environments; Organic matter; Paleoclimate; Precipitation; Radiocarbon dating; Radiometric dating; Reservoir construction; Reservoirs; Sediments; Temporal variations; Variability; Volcanoes; Wind; Altiplano; Argentina; Southern Hemisphere
• ISSN: 2628-3719; 2628-3697; 2628-3719
• DOI: 10.5194/gchron-5-333-2023

The high-altitude lakes of the Altiplano–Puna Plateau in the Central Andes commonly have large radiocarbon reservoir effects. This, combined with the general scarcity of terrestrial organic matter, makes obtaining a reliable and accurate chronological model based on radiocarbon ages a challenge. As a result, age–depth models based on radiocarbon dating are often constructed by correcting for the modern reservoir effect, but commonly without consideration of spatial and possible temporal variations of reservoir ages within the lake and across the basin. In order to get a better constraint on the spatial variability of the radiocarbon reservoir effects, we analyse 14C ages of modern terrestrial and aquatic plants from the El Peinado basin in the southern Puna Plateau, which hosts Laguna del Peinado fed by hydrothermal springs. The oldest
14C ages of modern samples (> 18 000 and > 26 000 BP) were found in hot springs discharging into the lake, likely resulting from the input of 14C-depleted carbon from old groundwater and 14C-free magmatic CO2. In the littoral and central part of Laguna del Peinado, 14C ages of modern samples were several thousand years younger (> 13 000 and > 12 000 BP) compared to the inflowing waters as a result of CO2 exchange with the atmosphere. Altogether, our findings reveal a spatial variability of up to 14 000
14C years of the modern reservoir effect between the hot springs and
the northern part of the Peinado lake basin. Temporal changes of reservoir
effects in sediment records are more difficult to quantify, but 14C ages from a short core from Laguna del Peinado may suggest temporal reservoir age variations of a few thousand years. This study has implications for accurate 14C-based chronologies for palaeoclimate studies in the Altiplano–Puna Plateau and similar settings. Our results highlight the need to consider spatial and likely also temporal variations in the reservoir effects when constructing age–depth models.