Biogeochemical Processes Controlling Oxygen and Carbon Isotopes of Diatom Silica in Late Glacial to Holocene Lacustrine Rhythmites
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Biogeochemical Processes Controlling Oxygen and Carbon Isotopes of Diatom Silica in Late Glacial to Holocene Lacustrine RhythmitesAutor(es)
Data
2010-05-19Cita bibliográfica
Armand Hernández, Roberto Bao, Santiago Giralt, Philip A. Barker, Melanie J. Leng, Hilary J. Sloane, Alberto Sáez, Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine rhythmites, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 299, Issues 3–4, 2011, Pages 413-425, ISSN 0031-0182, https://doi.org/10.1016/j.palaeo.2010.11.020. (https://www.sciencedirect.com/science/article/pii/S0031018210006966)
Resumo
[Abstract] Biogeochemical cycles and sedimentary records in lakes are related to climate controls on hydrology and catchment processes. Changes in the isotopic composition of the diatom frustules (δ18Odiatom and δ13Cdiatom) in lacustrine sediments can be used to reconstruct palaeoclimatic and palaeoenvironmental changes. The Lago Chungará (Andean Altiplano, 18°15′S, 69°10′W, 4520masl) diatomaceous laminated sediments are made up of white and green multiannual rhythmites. White laminae were formed during short-term diatom super-blooms, and are composed almost exclusively of large-sized Cyclostephanos andinus. These diatoms bloom during mixing events when recycled nutrients from the bottom waters are brought to the surface and/or when nutrients are introduced from the catchment during periods of strong runoff. Conversely, the green laminae are thought to have been deposited over several years and are composed of a mixture of diatoms (mainly smaller valves of C. andinus and Discostella stelligera) and organic matter. These green laminae reflect the lake's hydrological recovery from a status favouring the diatom super-blooms (white laminae) towards baseline conditions. δ18Odiatom and δ13Cdiatom from 11,990 to 11,530cal years BP allow us to reconstruct shifts in the precipitation/evaporation ratio and changes in the lake water dissolved carbon concentration, respectively. δ18Odiatom values indicate that white laminae formation occurred mainly during low lake level stages, whereas green laminae formation generally occurred during high lake level stages. The isotope and chronostratigraphical data together suggest that white laminae deposition is caused by extraordinary environmental events. El Niño-Southern Oscillation and changes in solar activity are the most likely climate forcing mechanisms that could trigger such events, favouring hydrological changes at interannual-to-decadal scale. This study demonstrates the potential for laminated lake sediments to document extreme pluriannual events.
Palabras chave
Oxygen isotopes
Carbon isotopes
Diatoms
Lacustrine sediments
Andean Altiplano
ENSO
Carbon isotopes
Diatoms
Lacustrine sediments
Andean Altiplano
ENSO
Descrición
Preprint version of the article.
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ISSN
0031-0182