Reconstructing seasonal to millennial climatic changes in northern subtropical Africa during the Holocene: Relationships between precipitation, vegetation and erosion dynamics inferred from laminated sediments from the Nile deep-sea fan

• Applicant: Dr. Cécile Blanchet
• Subject Area: Palaeontology
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 164374085

Sediments deposited on submarine deltas are key archives to reconstruct past changes in fluvial regime, which provide crucial information on changes of the past environments of the hinterland. Sediment core P362/2-33 was retrieved at 700 m water-depth on the Nile deep-sea fan (R/V Poseidon cruise P362/2) and has millimeter-scale laminations. Detailed 14C dating shows that the core covers the last 9,500 years, with laminated sediments being deposited at very high rates (up to 600 cm/ka) between 9,500 and 7,500 years ago. This time interval corresponds to the African Humid Period (AHP), which is known as an interval of enhanced river discharge in northern Africa. The laminated sediments of core P362/2-33 contain high amounts of terrigenous organic matter and minerals (mostly of fluvial origin) and provide the unique opportunity to investigate variations in fluvial regime of the Nile River at sub-seasonal time scales during the AHP. Together with my collaborators, I propose to measure the elemental content at mm-scale (using a X-Ray Fluorescence scanner) for core P362/2-33 and other laminated sediments from the region. The records will be analyzed using time series analytic tools (e.g., wavelet analyses) in order to characterize changes in frequency and magnitude of fluvial discharge through time and understand the mechanisms controlling changes in seasonality and hydrology. These unique sediments also allow to investigate the linkages and feedbacks between climate (seasonality), vegetation and erosion dynamics. To achieve this, we will use a combination of inorganic and organic geochemical methods. In order to determine the sources of the sediments and waters transported to the margin, it is proposed to apply neodymium and strontium isotope composition of the lithogenic fraction and foraminifera, respectively. The sources of organic mater and the amount and type of vegetation will be determined using the chemical and isotopic composition of specific lipid biomarkers (branched and isoprenoid tetraethers and plant waxes) originating from terrestrial soils and plants.

• DFG Programme: Research Grants