Where did the water come from? Wetlands and shallow lakes in semi‐arid dunefields from South America during the Pleistocene–Holocene transition

ALFONSINA TRIPALDI; IVANA LAURA OZÁN; GUILLERMO HEIDER; MARÍA JULIA ORGEIRA; STEVEN FORMAN

JOURNAL OF QUATERNARY SCIENCE

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 2024

0267-8179

ABSTRACT: Stabilized and active dunes and sand sheet deposits abound in a small lake‐dotted semi‐arid region ofthe Western Pampean Dunefield, Argentina. Here, a multi‐scale and multi‐proxy study of three sites, across ahydrologic gradient from lakes to a dryland with groundwater levels at more than 25 m depth, analyzes calcareousand ferruginous rhizoliths, calcareous crusts, hypocoatings, pedogenic carbonate and amorphous Mn‐oxideprecipitates within blowout dunes. These palustrine‐related features indicate significantly wetter conditions thatallowed the development of shallow lakes and expanding wetlands during the Pleistocene–Holocene transition,limited by associated optically stimulated luminescence ages between ca. 14.7 and 11.6 ka. These wetter conditions,also identified in other nearby proxy records, may be associated with a strengthened South American MonsoonSystem, potentially during the Younger Dryas Chronozone, though other geological, ecological and climatic forcingscannot be ruled out with available data. Such a scenario lacks a modern analogue, since current hydrologic excess,evidenced in the formation of lakes and new rivers, is not observed in the localities which record paleolakes. Thisstudy underlines the variable conditions for pronounced hydrologic excess in semi‐arid eolian environments inwestern Argentina with complex ecological, anthropogenic and climatic linkages. © 2024 John Wiley & Sons, Ltd.