Radiocarbon-dated multiproxy record of Holocene lacustrine sediments from Laguna Azul, southern Patagonia (Argentina)

Multiproxy investigations, including XRF core-scanning, sedimentology, stable isotopes, pollen and diatoms, of lacustrine sediments from Laguna Azul (52 °S) document a superior climatic control on environmental conditions: Position and strength of Southern Hemispheric Westerlies (SHW) have overprinted the lake's ontogeny. SHW influenced local hydroclimatic conditions on millennial to centennial timescales, which impact on water-column stratification as well as on lake-level fluctuations with feedbacks on lakeshore erosion, algal communities, trophic conditions, methanogenesis and authigenic mineral formation. Via the link between SHW and regional hydrology, our high-resolution environmental reconstruction documents hydroclimatic variability during the Holocene, which compares well with other South American records. We detected a cool and wet period from 11,600-10,100 cal. BP followed by an extended Early Holocene dry period (10,100 and 8300 cal. BP) with ectogenic meromixis and high salinity. From 8300 until c. 4000 cal. BP the influence of the SHW weakened resulting in less arid conditions and a deep freshwater lake. Since 4000 cal. BP, regional temperature decreased accompanied by intensification of SHW reaching its full strength at 3000 cal. BP. Superimposed on these multi-millennial SHW fluctuations, Laguna Azul additionally documents a centennial variability during the Late Holocene with dry spells centered around 3700, 2200, 1000 cal. BP and in the 20th century. Although less arid periods are evident between these dry spells, the only pronounced moist period is representative for the "Little Ice Age" (1460-1740 cal. BP). During the last two centuries, human impact slightly obscures the climatic signal. With this study, we introduce a new and high-resolution dataset of hydroclimatic variability from southeastern Patagonia, documenting a multi-millennial variability of SHW for the Holocene overprinted by higher frequency (centennial) hydrologic variability for the last ca. 4000 years