Quaternary environmental evolution of the Argentinean Pampa Deprimida based on mollusc and ostracod analysis

Abstract

Multiproxy analyses are efficient approaches in palaeoenvironmental reconstructions since they contemplate the different responses of various taxonomic groups to external changes. In this study, we analyse changes in molluscs and ostracod palaeocommunities to reconstruct the environments and their Holocene evolution in the Salado River, Pampa Deprimida of Argentina. We assessed the temporal and spatial variation of the assemblages from the Alberti-Pla, Ruta 30, and Vientos de Mar localities through various analytical techniques, including analysis of similarity (ANOSIM) and ordination methods such as non-metric multidimensional scaling (NMDS), detrended correspondence analysis (DCA), and principal component analysis (PCA). Eleven species of gastropods were identified, among which Heleobia parchappii, Biomphalaria peregrina, and Succinea meridionalis stand out for their abundance. Nine species of ostracods were recognised, with Limnocythere cusminskyae, Cypridopsis vidua, Heterocypris similis, and Cyprideis salebrosa being the most important. The changes in the assemblages allowed us to infer the paleoenvironmental evolution in the area. During the Late Pleistocene and Early Holocene, drier conditions led to ephemeral, marshy freshwater environments with fluctuating water levels and salinities. In the Late Holocene, increased precipitation caused water levels to rise, resulting in more stable and interconnected freshwater environments.