Paleoenvironmental changes in southern South American dust sources during the last glacial/interglacial transition: Evidence from clay mineral assemblages of the pampean loess

Abstract

Paleoclimatic reconstruction is critical for understanding present-day climate and for testing models that are currently used to predict future climatic changes. Different climatic conditions produce different clay minerals that can be recorded in geological archives providing insights into past weathering scenarios. However, in southern South America, scarce information is available from clay mineral assemblages found in aeolian sediments, such as loess deposits. Moreover, there is a lack of studies employing clay minerals for paleoclimatic reconstruction at dust sources and loess deposits. Therefore, this work explores clay mineral composition of modern dust source areas in southern South America and in the pampean loess records to gain insight into paleoenvironmental conditions prevailing during the late Pleistocene-early Holocene in the region. Clay minerals recovered from the loess deposits are of an allochthonous origin, implying their formation at the ‘arid diagonal’, then blown away, and deposited downwind in the Pampas without post-depositional changes. Clay mineral assemblages indicate that these minerals and rare earth elements (REE) analyzed in two loess sections of the Pampean Plain helped to reconstruct past climatic scenarios in the dust source areas during the transition from the last glacial to the current interglacial period. Furthermore, our work contributes to the assessment of the strengthening/weakening of the different South American dust sources in light of recent published geochemical and textural evidence.