Multiproxy reconstruction of environmental change from the late Pliocene to the Late Pleistocene in the Sauce Grande River basin, Argentina

Abstract The Sauce Grande River Basin (Buenos Aires Province, Argentina) presents a late Pliocene–Holocene sedimentary succession that preserves key evidence of Quaternary paleoenvironmental change in the southern Pampas. This study integrates stratigraphy, sedimentology, paleopedology, geochemistry, mineralogy, and stable isotope data to reconstruct paleoenvironmental evolution from the late Pliocene to the Late Pleistocene. Three paleosol types (Calcisols, Calcic Protosols, and Protosols) were identified and characterized through field descriptions, micromorphology, and molecular indices. Their development reflects shifts in landscape stability, sediment supply, and soil moisture regimes, consistent with glacioeustatic fluctuations and climatic oscillations during the late Plio-Pleistocene transition and the Quaternary. Stable isotope analyses of pedogenic carbonates reveal a trend from C₃-dominated vegetation under more humid conditions in the late Pliocene–Early Pleistocene, to more arid Late Pleistocene–Holocene environments, with increased δ 13 C values indicating reduced vegetation density and a higher potential contribution of C₄ plants. These findings align with palynological and faunal evidence, highlighting the value of paleosols as sensitive indicators of environmental change. The multiproxy approach adopted here provides new insights into soil formation dynamics and Quaternary palaeoecological transitions in non-glaciated midlatitude settings of South America.