Paleoenvironmental reconstruction of the semi-arid Chaco region of Argentina based on multiproxy lake records over the last six hundred years

In this paper, we analyze the paleoclimatic and paleoenvironmental evolution of Laguna Yema in semi-arid Chaco region of Argentina over the past six hundred years. High resolution multiproxy studies of lake sediments utilize analyses of lithology, mineralogy, geochemistry, palynology, and are constrained by radiocarbon and gamma spectrometry dating. Laguna Yema sediments were mainly composed of well stratified fine sediments (silts and clays), with variable proportions of quartz, clays (illite) and feldspar (microcline and albite). Twelve light and heavy geochemical elements were registered. Most elements (Al, Si, K, Ti, Fe, Rb, Ba, and Br) are associated with illite and albite. Different material transport processes related to the changes in aridity and humidity of the basin were identified using the main mineralogical origins of geochemical elements. Palynological records indicate cycles of contraction and expansion of the lake, with an increase in concentration of Alternanthera aquatica during wet periods (expansion of lake), and an increase in Ambrosia, Poaceae and fern spores during dry periods (contraction of lake). These changes are linked to fluctuations in moisture conditions in the Subandean Mountains and semi-arid Chaco regions, in response to interactions between the South American Monsoon System (SAMS) and the South American Low Level Jet (SALLJ), which send warm and humid air to northern Argentina. In a regional context, the Laguna Yema records are in accordance with the analyses of the temporal and spatial pattern of moisture distribution for the last six centuries. © 2019 Elsevier B.V.The Fundación BBVA funded the research in Laguna Yema through the Project “Past, Present and Future of Natural and Human Communities of the Dry Forest of South America: The Case of the Argentine Dry Chaco”. The Institute of Earth Sciences Jaume Almera (ICTJA-CSIC) and the University of Barcelona are recognized for providing the facilities for mineralogical and geochemical analyses, respectively. The Laboratory of Palynology of the School of Agricultural Sciences (UNJu) and Grupo Yavi de Investigaciones Científicas collaborated in the processing of pollen samples. We are grateful to Juan Padañu and family for helping us with the logistics and to the CEDEVA Laguna Yema for the facilities and local information. We also wish to thank Jamie Bookwalter for her corrections in the manuscript. We thank anonymous reviewers for their comments and criticisms that improved the manuscript.Peer reviewe