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- Title
Stable isotopic record of hydrological changes in subtropical Laguna Mar Chiquita (Argentina) over the last 230 years.
- Authors
Piovano, Eduardo L.; Ariztegui, Daniel; Bernasconi, Stefano M.; McKenzie, Judith A.
- Abstract
Laguna Mar Chiquita, a highly variable closed saline lake located in the Pampean plains of central Argentina, is presently the largest saline lake in South America ( 6000 km2). The availability of historical, instrumental lake-level and salinity data for the past 100 years allows for the calibration of the isotopic archive recorded in the lake sediments. Prolonged intervals with either negative or positive hydrological balances have severely modified lakewater levels, salinity and primary productivity, and have also controlled the isotopic composition of both the authigenic carbonate (d18 Ocarb and d13 Ccarb) and sedimentary organic matter (d13 Com). Extensive evaporation during lowstand stages results in an enrichment of 18 O and 13C in the lake waters, and is recorded in the sediments as the most positive d18 O carb and d13 C carb compositions (0.0 % and 1.9 % , respectively). Conversely, more negative d18 O carb and d13 Ccarb values (1.8% and 3.8%, respectively) are the result of increasing freshwater input into the lake system. The d13 Com values are related to the isotopic composition of the dissolved inorganic carbon pool and the carbonate equilibrium of the lake water. Relatively low d13 Com values correspond with high lake levels, low salinity, low alkalinity and high lake productivity. High salinity during lowstands diminishes the amount of primary production and the d13 Com value is correspondingly high. The calibrated isotopic model was extrapolated to reconstruct precipitation-evaporation variability from the end of the 'Little Ice Age' (c. AD1770) to the present. Low water levels predominated until the last quarter of the twentieth century, when a positive hydrological balance without equivalent in the previous history of Laguna Mar Chiquita became dominant.
- Subjects
ARGENTINA; PALEOHYDROLOGY; SALT lakes; STABLE isotopes; PLEISTOCENE stratigraphic geology; SEDIMENTS
- Publication
Holocene, 2004, Vol 14, Issue 4, p525
- ISSN
0959-6836
- Publication type
Article
- DOI
10.1191/0959683604hl729rp