A high-resolution palaeoclimate record for the last 4800 years from lake la Brava,SE pampas plains,Argentina |
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| Institution: | 1. Instituto de Física Arroyo Seco, Universidad Nacional del Centro de, la Provincia de Buenos Aires, Pinto 399, 7000 Tandil, Argentina;2. Consejo Nacional de Investigaciones Científicas y, Técnicas, Rivadavia 1917, C1033AAJ, Buenos Aires, Argentina.;3. Estación Experimental de Aula Dei, CSIC. Av. Montañana 1.005. 50059, Zaragoza, España;4. Instituto de Investigaciones Marinas y Costeras, Laboratorio de Paleoecología y Palinología, Universidad Nacional de Mar del Plata, Funes 3250, B7600GYI Mar del Plata, Argentina;5. Instituto Antártico Argentino (IAA), Cerrito 1248, Buenos Aires, Argentina;6. Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA |
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| Abstract: | Climatic changes are reflected in variations of different parameters. Sequences of lake sediments are good sources of this information because they provide continuous and detailed records of palaeoclimatic changes. In order to determine the changes in climate in SE Pampas plain, in this paper we present a series of rock magnetic studies performed on a bottom core collected from Lake La Brava (Argentina).In order to establish lake level variations, we also measure total sulphur, organic and inorganic carbon (TS, TOC and TIC) content, alkaline elements, light and heavy metals and changes in vegetation communities. Five radiocarbon age determinations were made from samples of organic-rich clay and calibrated ages were calculated. The averaged sediment accumulation rate is 1.3 mm/yr and the sequence represents a temporal extent of about 4800 calibrated years before the present (cal. BP).The main aim was to reconstruct the hydrological balance of the lake, the changes in erosional strength and sediment supply within the catchment area since the Middle Holocene, and to explore the extent to which these may be linked to changes in climate and/or human activities. The results of this work and previous studies suggest periodic changes from cooler to warmer and humid conditions. Relationships between submerged and emergent plants are consistent with the behaviour of magnetic susceptibility. TOC changes suggest wet environment during magnetic enhancement. Floods and lower lake level events were identified in detail. Changes in sediment contribution and depositional processes for the last 50 cal. BP are caused by human impact, particularly by the use of natural resources. |
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| Keywords: | palaeoclimatic changes rock magnetism sediment cores South America lake level dry events |
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