CICTERRA   20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
artículos
Título:
Palaeolimnology of Lake Hess (Patagonia, Argentina): multi-proxy analyses of short sediment cores
Autor/es:
PIERO GUILIZZONI Æ JULIETA MASSAFERRO Æ ANDREA LAMI Æ EDUARDO LUIS PIOVANO Æ SERGIO RIBEIRO GUEVARA Æ STELLA MARIS FORMICA Æ ROMINA DAGA Æ ANDREA RIZZO Æ STEFANO GERLI
Revista:
HYDROBIOLOGIA
Editorial:
SPRINGER
Referencias:
Año: 2009 vol. 631 p. 289 - 302
ISSN:
0018-8158
Resumen:
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 23.2 mg cm−2 y−1 (0.15 cm y−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 (83 cm) identify three main phases
of change. From the bottom up to 42 cm (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 17701850), pigment concentrations were very low. From 42 cm to ca. 25 cm (ad
18001940), 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 25 cm
(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.