NORTHEAST AFRICAN PLIO-PLEISTOCENE CLIMATE PATTERNS USING PLANT WAX ISOTOPES FROM MEDITERRANEAN SAPROPELS (Invited Presentation)

Long-term climate variations and secular changes over the Plio-Pleistocene have been linked to hominin evolution in Africa. These patterns, though, have been difficult to quantify in tandem in well-dated and continuous archives. The iconic sapropels of the Mediterranean are organic-rich sediment layers preserved during intensified northeast African rainfall, runoff, and subsequent stratification of sea water. They provide an incredible archive of precessionally paced African monsoon strength over millions of years and an important context for hominin evolution. However, due to their binary nature, it is difficult to extract information on trends, shifts, and the amplitude of climate variability during the Plio-Pleistocene, when substantial changes occurred in ice volume boundary conditions, sea surface temperature gradients, and terrestrial ecosystems. Here we present plant wax hydrogen and carbon isotope records derived from astronomically dated sediment cores from ODP Sites 966 and 967 in the eastern Mediterranean Sea. Plant waxes, which are sourced from the eastern Sahara (Rose et al., 2016), were sampled from each sapropel over the last 4.5 myr to obtain a record consisting of the wet endmembers from each insolation cycle. Despite capturing only the strong African monsoon intervals, we find a large range in plant wax hydrogen isotope values and a significant aridification shift around the mid-Pleistocene transition at ~800 ka. Through time series analyses, we uncover prominent 400 kyr and 100 kyr eccentricity cycles, indicating that low frequency variability is crucial for modulating northeast African climate. This finding is in agreement with the evidence for synchronous East African deep lake pulses (Maslin et al., 2014 and references therein), and our isotope study provides higher resolution, a direct connection with quantitative terrestrial vegetation estimates, and more detailed evidence for periodic wet and high-variability intervals throughout the Plio-Pleistocene, which may be linked with enhanced hominin evolutionary transitions.