Reconstructing tropical African hydrology using hydrogen isotope ratios of lacustrine sedimentary biomarkers: a calibration transect across Cameroon
Abstract
Compound-specific hydrogen isotope ratio analysis (δD) of ancient leaf-wax lipids has emerged as a reliable palaeohydrological proxy since it may provide a record of isotopic properties of ancient plant water, which may indirectly reflect isotopic signatures of plant source water. As demonstrated for material collected in several mid- and high-latitude lacustrine environments, there is a tight relationship between leaf-wax δD and source-water δD. In another hand, for the Tropics, where both vegetation and processes associated with isotope fractionation in the hydrologic system strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. The need of such calibration is further emphasized since leaf-wax lipid δD signatures are increasingly used to reconstruct past changes in tropical hydrology. Due to our limited understanding of the factors controlling leaf-wax δD values in tropical ecosystems, any of such reconstructions are only of qualitative nature at best. Here, we present results of compound-specific hydrogen isotope ratios of lipids deposited in lake sediments from tropical Africa. The main goal of this project is to identify the environmental variables and plant physiological processes that control the hydrogen isotopic composition of leaf-wax lipid biomarkers in the Tropics, and to develop a robust framework for the quantitative application of compound-specific hydrogen isotopes in tropical Africa. For this purpose, a 10°-long latitudinal transect across Cameroon was chosen because it encompasses a wide range of contrasting vegetation classes and climates that are representative for tropical Africa. Here, we show preliminary data of the δD values of selected biomarkers from recent lake surface sediments collected in Cameroon. These data are further compared with the δD values of lake water, xylem water, and rainfall along this transect.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP21C1706G
- Keywords:
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- 1041 GEOCHEMISTRY / Stable isotope geochemistry;
- 1055 GEOCHEMISTRY / Organic and biogenic geochemistry;
- 1845 HYDROLOGY / Limnology;
- 3344 ATMOSPHERIC PROCESSES / Paleoclimatology