Holocene palaeoclimates of southern Patagonia: limnological and environmental history of Lago Cardiel, Argentina

Abstract

Multiproxy palaeoenvironmental and palaeolimnological analyses of two Holocene-age sediment cores from the margin of Lago Cardiel, a 76 m deep, closed-basin lake in southern Patagonia (latitude 49°S), provide information on lake-level changes that can be related to regional palaeoclimate scenarios. Sedimentol ogic (magnetic susceptibility, organic and inorganic carbon content) and environmental indicators (pollen, dia toms, ostracodes and stable isotopes on ostracodes) show lake levels markedly higher than today during the early Holocene, following a rapid lake-level rise after a desiccation phase prior to 11000 BP. After about 6000 BP, lake levels were generally lower, but underwent repeated fluctuations. These inferred changes support the previously proposed view that the southern westerly stormtracks were focused (zonal) north of latitude 50°S during the early Holocene, allowing for Antarctic cold fronts to bring easterly moisture to southern Patagonia, whereas during the late Holocene the stormtracks shifted seasonally, with an overall more meridional behaviour, resulting in less and more variable moisture at these latitudes.

Transient simulations, empirical reconstructions and forcing mechanisms for the Mid-holocene hydrological climate in southern Patagonia

“…Correlations are highest in JJA, where the strength of the westerly winds explains approximately 25% of the precipitation variability. Thus, in general our results confirm the dynamical processes that have already been qualitatively proposed by Markgraf (1993) and Markgraf et al (2003). However, the fact that we found only a moderately strong circulation-precipitation link does not support the hypothesis of a pronounced link between zonal winds and precipitation in south-eastern Patagonia that is often assumed in the context of proxy-reconstructions.…”

“…Markgraf 1993;Schäbitz 1999;Lamy et al 2001;Jenny et al 2003;Markgraf et al 2003;Mancini et al 2005;Gilli et al 2005a,b). These hypotheses were usually derived in a two step process.…”

“…Concerning the driving mechanisms of the lake level variations at Lago Cardiel, Markgraf et al (2003) argue that a shift within the position of the stormtracks controls the moisture transport into south-eastern Patagonia.…”

“…Paleoclimate studies in the vicinity of LPA have also been undertaken by Markgraf et al (2003) for Lago Cardiel, 330 km to the north of LPA. For the mid-Holocene around 6 ka BP lake levels are reconstructed to have been generally lower but with repeated fluctuations.…”

Geoarchaeological and Paleoenvironmental context of the human settlement in the Eastern Tandilia Range, Argentina

“…Consequently, they are well-established indicators for both monitoring present changes in water condition, and tracking past environmental changes through the analysis of the assemblages preserved in sediments (see Smol and Stoermer, 2010). In Argentina, continental diatoms have been used to infer paleoenvironments in southern (Zárate et al, 2000;Hassan et al, 2004), and western Pampas (González and Maidana, 1998), and Patagonia (Markgraf et al, 2003;Mayr et al, 2005).…”