Relationships between Holocene sea-level variations,trophic development,and climatic change in Negra Lagoon,Southern Uruguay |
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| Authors: | R?Bracco H?Inda L?del Puerto C?Casti?eira P?Sprechmann Email author" target="_blank">F?García-RodríguezEmail author |
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| Institution: | (1) Facultad de Química (UDELAR), Laboratorio 14C, Comisión Nac. de Arqueología (M.E.C.) -- Cátedra de Radioquímica, Gral. Flores 2124 Montevideo, Uruguay;(2) Facultad de Ciencias, UNICIEP, Iguá 4225, 11400 Montevideo, Uruguay;(3) División Antropología, Museos Naturales de Historia Natural y Antropología, Instrucciones 948, Montevideo, Uruguay;(4) Facultad de Ciencias, Sección Paleontología, Iguá 4225, 11400 Montevideo, Uruguay |
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| Abstract: | Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142 km2 coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000 yr BP), cool–dry climatic conditions were established. After ~4000 yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700 yr BP. Such climatic amelioration led to increases in trophic state. |
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| Keywords: | Climatic change Diatoms Holocene Opal Phytoliths Sea level change Trophic state Uruguay |
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