Last glacial hydrological variations at the southern margin of sub-tropical North America and a regional comparison

International audience; Geochemical and magnetic characteristics of sediments from paleolake La Salada provideinformation about the last glacial hydrological conditions at the southern margin of sub-tropical North America.Proxy records of runoff, lake water salinity, brine composition and provenance of organic matter are based onmulti-element concentration, magnetic susceptibility, mineralogy, carbonate content and C/N relation. Runoff washigher than average during ca. 43–36k cal a BP and at ca. 33k cal a BP. A shift in mineralogical assemblage fromcalcite > protodolomite–halite to protodolomite–gaylussite suggests that the brine composition changed fromCa–(Mg–Na)–HCO3–(Cl) to Mg–Na–Ca–HCO3 because of more runoff after the desiccation event at ca. 28k cal aBP. In general, organic matter deposited during the intervals of more runoff and deeper lake conditions weresourced from lacustrine phytoplankton. The contribution of terrestrial vegetation dominates during the intervals ofreduced runoff. Comparison with other records provides a regional perspective of moisture variability. Humidconditions at ca. 33k cal a BP could be due to more summer precipitation in northern Mexico as well as increasedwinter rainfall in the south-western USA.