Biomarker records of late Neogene changes in northeast African vegetation

Open savannah grasslands (dominated by C-4 plants) became a significant component of northeast African vegetation during the late Neogene. We present molecule-specific carbon isotopic measurements of terrestrial plant biomarkers preserved in marine sediments off northeast Africa that allow reconstruction of orbital-scale vegetation changes in short time windows over the past 9.4 m.y. The biomarker data show large-amplitude vegetation variability as early as 3.8 Ma, with the greatest C-4 expansion occurring after 3.4 Ma. We sampled orbital-scale oscillations of up to 5 parts per thousand, almost as large as the observed late Neogene range of 7 parts per thousand, suggesting that large and repeated oscillations between more open and more closed landscapes were an important aspect of northeast African vegetation change during the past 4 m.y.