Late Quaternary paleohydrological conditions in the drylands of northern Mexico: a summer precipitation proxy record of the last 80 cal ka BP

We present a late Quaternary multi-proxy record from the paleolake Babicora in order to understand the influence of North American Monsoon (NAM) and westerly winter storms on the paleohydrological budget of the drylands of northern Mexico. Stratigraphy, 14C chronology, mineral magnetism and geochemistry of the 976 cm long sediment core were used to reconstruct the hydrological conditions over the last 80 cal ka BP. The inverse relationship between the proxy records of runoff into Babicora and winter precipitation in southwestern USA indicate the minimal influence of westerly winter storms at 29°N during the Last Glacial period. Westerly winds transported minimally chemically altered sediments from the dry watershed during the cold stadials and the basin received more than average runoff as a result of a stronger NAM during the warm interstadials. The highest pluvial discharge occurred prior to 58 cal ka BP and terrestrial plants became the major contributor to organic matter deposited between 71 and 53 cal ka BP. Over the last 40 cal ka BP, the high amplitude fluctuations in runoff and lake water salinity mirrored an unstable summer rainfall regime.