| Title | Palaeolimnology of Lake Hess (Patagonia, Argentina): Multi-proxy analyses of short sediment cores |
| Abstract | In contrast with the extensive palaeolimnological studies carried out in North America and Europe, relatively few studies have described the anthropogenic and/or climate impacts in Patagonian lakes. We addressed these issues by analysing geochemistry, lithology, pigments and chironomid remains from sediment cores collected from Lake Hess (41°22?20?S, 71°44?0?W) located in the Nahuel Huapi National Park in northern Patagonia. The aim of this study is to provide a palaeoenvironmental and climate reconstruction of the past ca. three centuries for this cold oligotrophic, quasi-pristine lake which receives meltwaters from the Tronador ice cap. Chronology was based on 137Cs and 210Pb measurements of the upper sediments, and the inferred sedimentation rate of 23.2mgcm-2y-1 (0.15cmy-1) was consistent with both sets of measurements. The sediment from Lake Hess was rich in tephra deposits particularly evident in the lower part of the cores. Tephras are valuable to use for core correlation and can be traced through peaks in the magnetic susceptibility (MS) profiles. Results from the multiproxy analyses in the longest core (83cm) identify three main phases of change. From the bottom up to 42cm (ca. ad 1800), the sediment is composed of light-grey organically rich clays. Both pigments and chironomids suggest variable trends in productivity and precipitation regime. At the end of the Little Ice Age chronozone (ad 1770-1850), pigment concentrations were very low. From 42cm to ca. 25cm (ad 1800-1940), the sedimentary record is composed of alternating black and dark organic-matter rich mud with variable amounts of macrophyte remains. Pigment concentrations and chironomid head capsule counts were also very low. These facies are composed of very fine plastic sediments with some faintly laminated intervals and an organic matter composition gradually decreasing towards the top of the zone. A sharp change occurs at 25cm (ca. ad 1940) showing a strong increase in organic matter content, algal nutrients and plant pigments together with a change in the chironomid assemblages. This might document a change in the trophic condition of the lake associated with changes in erosion/deposition rates. Although there are records of human impact in the area studied, involving the use of fires, most of the observed chemical and biological changes in Lake Hess sediment sequence were interpreted in terms of climate changes, especially to changes in moisture balance brought about by variations in the strength of the westerlies. |
| Source | Hydrobiologia (The Hague. Print) 631 (1), pp. 289–302 |
| Keywords | ChironomidsPalaeolimnologyPatagoniaPigmentsSouth America |
| Journal | Hydrobiologia (The Hague. Print) |
| Editor | Kluwer Academic Publishers, Boston, Paesi Bassi |
| Year | 2009 |
| Type | Articolo in rivista |
| DOI | 10.1007/s10750-009-9818-5 |
| Authors | Guilizzoni, Piero; Massaferro, Julieta; Lami, Andrea; Piovano, Eduardo Luis; Guevara, Sergio Ribeiro; Formica, Stella Maris; Daga, Romina; Rizzo, Andrea; Gerli, Stefano |
| Text | 346898 2009 10.1007/s10750 009 9818 5 ISI Web of Science WOS 000271240700018 Scopus 2 s2.0 67349213679 Chironomids Palaeolimnology Patagonia Pigments South America Palaeolimnology of Lake Hess Patagonia, Argentina Multi proxy analyses of short sediment cores Guilizzoni, Piero; Massaferro, Julieta; Lami, Andrea; Piovano, Eduardo Luis; Guevara, Sergio Ribeiro; Formica, Stella Maris; Daga, Romina; Rizzo, Andrea; Gerli, Stefano Consiglio Nazionale delle Ricerche; Consejo Nacional de Investigaciones Cientificas y Tecnicas; Universidad de Cordoba; Comision Nacional de Energia Atomica Argentina In contrast with the extensive palaeolimnological studies carried out in North America and Europe, relatively few studies have described the anthropogenic and/or climate impacts in Patagonian lakes. We addressed these issues by analysing geochemistry, lithology, pigments and chironomid remains from sediment cores collected from Lake Hess 41°22 20 S, 71°44 0 W located in the Nahuel Huapi National Park in northern Patagonia. The aim of this study is to provide a palaeoenvironmental and climate reconstruction of the past ca. three centuries for this cold oligotrophic, quasi pristine lake which receives meltwaters from the Tronador ice cap. Chronology was based on 137Cs and 210Pb measurements of the upper sediments, and the inferred sedimentation rate of 23.2mgcm 2y 1 0.15cmy 1 was consistent with both sets of measurements. The sediment from Lake Hess was rich in tephra deposits particularly evident in the lower part of the cores. Tephras are valuable to use for core correlation and can be traced through peaks in the magnetic susceptibility MS profiles. Results from the multiproxy analyses in the longest core 83cm identify three main phases of change. From the bottom up to 42cm ca. ad 1800 , the sediment is composed of light grey organically rich clays. Both pigments and chironomids suggest variable trends in productivity and precipitation regime. At the end of the Little Ice Age chronozone ad 1770 1850 , pigment concentrations were very low. From 42cm to ca. 25cm ad 1800 1940 , the sedimentary record is composed of alternating black and dark organic matter rich mud with variable amounts of macrophyte remains. Pigment concentrations and chironomid head capsule counts were also very low. These facies are composed of very fine plastic sediments with some faintly laminated intervals and an organic matter composition gradually decreasing towards the top of the zone. A sharp change occurs at 25cm ca. ad 1940 showing a strong increase in organic matter content, algal nutrients and plant pigments together with a change in the chironomid assemblages. This might document a change in the trophic condition of the lake associated with changes in erosion/deposition rates. Although there are records of human impact in the area studied, involving the use of fires, most of the observed chemical and biological changes in Lake Hess sediment sequence were interpreted in terms of climate changes, especially to changes in moisture balance brought about by variations in the strength of the westerlies. 631 Published version http //www.scopus.com/record/display.url eid=2 s2.0 67349213679 origin=inward Articolo in rivista Kluwer Academic Publishers 0018 8158 Hydrobiologia The Hague. Print Hydrobiologia The Hague. Print Hydrobiologia The Hague. Print Hydrobiologia. The Hague. Print Hydrobiologia Dordrecht The Hague. Print Hydrobiologia Boston The Hague. Print Hydrobiologia London The Hague. Print GERLI STEFANO piero.guilizzoni GUILIZZONI PIERO andrea.lami LAMI ANDREA |
