FP 28: High-resolution reconstruction of late-Glacial and Holocene climate variability in equatorial East Africa based on laminated lake sediments from Mt. Kilimanjaro

• Applicant: Professor Dr. Achim Brauer, since 1/2008
• Subject Area: Palaeontology
• Term: from 2005 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5447419

• Final Report Year: 2012

Final Report Abstract

The main goals of the GFZ part of the project were sediment coring, core opening, documentation and storage as well as detailed micro-facies analyses to develop novel sedimentological proxies and a robust chronology through varve counting. First, the sediment cores have been described in detail based on macroscopic inspection. Based on these data and in combination with high-resolution measurement of magnetic susceptibility a 21.6 m long continuous composite (master) profile has been established. This composite profile was the base for all further investigation by all project partners. In addition, an intensive lake monitoring has been set up in order calibrate sediment data with climatic variables. This lake monitoring included a monthly sediment trap, a weather station and mapping of the lake catchment. The resulting data enabled to characterize the present day state of Lake Challa and to provide a sophisticated interpretation of various proxy data in terms of climatic signals. We consequently followed a multi-proxy approach including stable isotopes (δ15N; δ13Corg; δ18O, δ18Ocarb, δ13C), µ-XRF major element scanning, standard X-Ray fluorescence and X-Ray diffraction for mineral determination. In addition, common standard carbon and nitrogen analyses were carried out (total carbon, total organic carbon, inorganic carbon, total nitrogen). Sedimentological investigations focused on microscopic analyses including annual layer counting and seasonal layer thickness measurements. More than 200 large-scale petrographic thin sections (10 cm long) have been analysed in great detail. For the first time, it thus was possible to prove and document annual layer (varve) formation in a tropical lake based on combined micro-facies data and sediment monitoring. This new high-resolution data ultimately enabled a very detailed comparison of inter-annual climate variability during warm, interglacial and cold glacial climate conditions. These high-resolution climate reconstruction ideally complemented climate change signals on longer time scales.

Publications

• (2006). CHALLACEA: High-resolution, multi-proxy climate reconstruction for equatorial East Africa (21 ka BP to present) from laminated lake sediments near Mt. Kilimanjaro. EGU General Assembly, Vienna (Austria), 02.04.2006-07.04.2006
  Verschuren, D., Haug, G., Sinninghe-Damste, J., van Geel, B., Conley, D., De Batist, M., Kristen, I., Fagot, M., Lyaruu, A., Milne, I., Hus, J., Keppens, E., van der Plicht, J., Hus, J., Nowaczyk, N.R., Mingram, J., Brauer, A., Cumming, B.F. & Russell, J.M.
  
• (2006). Stratigraphy and geochemistry of post-Glacial lacustrine sedimentation (21 ka BP to present) in Lake Challa, East Africa. EGU General Assembly, Vienna (Austria), 02.04.2006-07.04.2006
  Kristen I., D. Verschuren, G.H. Haug, U. Roehl, N.R. Nowaczyk
  
• (2007). Abrupt lakelevel changes in Lake Challa (East-Africa) revealed by high-resolution seismic stratigraphy: relationship to global paleoclimatic events during the last glacial-interglacial cycle? 4th International Limnogeology Congress, Barcelona (Spain) 11.07.2007–14.07.2007
  Moernaut, J., Verschuren, D., Kristen, I., Fagot, M. & De Batist, M.
  
• (2008). A 25,000 years climate record from the East African equator: Half-precessional climate forcing and the history of temperature and hydrological change. EGU General Assembly, Vienna (Austria), 13.04.2008-18.04.2008
  Verschuren, D., Sinninghe Damste, J.S., Haug, G., Kristen, I., Moernaut, J., Milne, I., Wolff, C., Fagot, M., van Geel, B., Blaauw, M.
  
• (2008). Half-precessional climate forcing of Indian Ocean monsoon dynamics on the East African equator. Final EuroCLIMATE Conference, Giens (France), 29.-30.09.2008
  Verschuren D., J.S. Sinninghe Damsté, J. Moernaut, I. Milne, I. Kristen, M. Fagot, G. Haug, M. Blaauw
  
• (2008). High-resolution age-depth modelling of the Lake Challa sediment record, 25,000 kyr BP to present (Mt. Kilimanjaro, Kenya/Tanzania). Final EuroCLIMATE Conference, Giens (France), 29.-30.09.2008
  Blaauw M., D. Verschuren, B. van Geel, I. Kristen, A. Lyaruu, J. van der Plicht
  
• (2008). High-resolution seismic stratigraphy as a tool for reconstructing abrupt lake-level changes over the last glacial-interglacial cycle: Lake Challa (Equatorial East Africa). Final EuroCLIMATE Conference, Giens (France), 29.-30.09.2008
  Moernaut J., Verschuren D., Charlet F., Kristen I., Fagot M. van der Plicht J. & De Batist M.
  
• (2008). Lake Challa (Kenya/Tanzania) sediments – a varved climate archive of environmental variability in equatorial East Africa of the last 25,000 years. Final EuroCLIMATE Conference, Giens (France), 29.-30.09.2008
  Wolff C., G. Haug, B. Plessen, I. Kristen, D. Verschuren
  
• (2008). Lake Challa (Mt. Kilimanjaro) sediments as recorder of present and past seasonality in equatorial East Africa. Final EuroCLIMATE Conference, Giens (France), 29.-30.09.2008
  Kristen I., C. Wolff, G. Schettler, P. Dulski, R. Naumann, G. Haug, M. Blaauw, D. Verschuren
  
• (2009). Half-precessional dynamics of monsoon rainfall near the East African Equator. Nature, 462, (7273), 637-641
  Verschuren, D., Sinninghe Damsté, J. S., Moernaut, J., Kristen, I., Blaauw, M., Fagot, M., Haug, G. H.
  
• (2009). Investigations on rainfall variability during the late Quaternary based on geochemical analyses of lake sediments from tropical and subtropical southern Africa. PhD thesis, Universität Potsdam, 124 p.
  Kristen, I.
  
• (2010). A 25,000-year record of climate-induced changes in lowland vegetation of eastern equatorial Africa revealed by the stable carbonisotopic composition of fossil plant leaf waxes. Earth and Planetary Science Letters, 302, (1- 2), 236-246
  Sinninghe Damsté, J. S., Verschuren, D., Ossebaar, J., Blokker, J., van Houten, R., van der Meer, M. T. J., Plessen, B., Schouten, S.
  
• (2010). The seismic-stratigraphic record of lake-level fluctuations in Lake Challa: Hydrological stability and change in equatorial East Africa over the last 140 kyr. Earth and Planetary Science Letters, 290, (1-2), 214-223
  Moernaut, J., Verschuren, D., Charlet, F., Kristen, I., Fagot, M., De Batist, M.
  
• (2011). High-resolution 14C dating of a 25,000-year lakesediment record from equatorial East Africa. Quaternary Science Reviews, 30, (21-22), 3043-3059
  Blaauw, M., van Geel, B., Kristen, I., Plessen, B., Lyaruu, A., Engstrom, D. R., van der Plicht, J., Verschuren, D.
  
• (2011). Reduced Interannual Rainfall Variability in East Africa During the Last Ice Age. Science, 333, (6043), 743-747
  Wolff, C., Haug, G. H., Timmermann, A., Sinninghe Damsté, J. S., Brauer, A., Sigman, D. M., Cane, M. A., Verschuren, D.