Abstract:
The Masoko maar (southern Tanzania) provides one of the most continuous Late Quaternary lacustrine sedimentary records from Africa. A detailed chronostratigraphic framework coupled with sedimentological and magnetic measurements allows us to construct a 30-year resolution continuous sedimentary sequence covering the last 45,000 years and to address local depositional environment and climate variability in the tropical Southern Africa. Based on present-day observations and measurements, our results indicate that the low-field magnetic susceptibility of the sediment is highly controlled by climate-driven processes (wind-stress and/or lake-level amplitude changes) acting on the titanomagnetite-rich shoreline reservoir. The tephra- and turbidite-free magnetic susceptibility record is strongly modulated by a persistent multi-decadal to centennial variability (∼80 to 200 years), probably linked to the Gleissberg and Suess cycles of solar activity. At lower frequency, the variability of deposition is controlled by the precessional cycle and its harmonics, suggesting a dominant multi-millennial forcing of low-latitude insolation on climatic changes in tropical Southern Africa. Inferred wetter conditions during the Last Glacial Maximum and the Younger Dryas at Masoko (9°S) indicate southward shifts of the Intertropical Convergence Zone associated with the North Atlantic glacial dynamics, and/or contrasted hydrological changes in the Rungwe highlands compared to the neighbouring areas. Finally, former regional transfer function between diatom assemblages and water chemistry suggested
