HR: 14:55h
AN: PP13C-06    [Abstracts]
TI: Orbital-Scale Vegetation Variability in Northeast Africa
AU: * Feakins, S J
EM: singram@ldeo.columbia.edu
AF: LDEO, Columbia University, PO BOX 1000, Palisades, NY 10964 United States
AU: deMenocal, P B
EM: peter@ldeo.columbia.edu
AF: LDEO, Columbia University, PO BOX 1000, Palisades, NY 10964 United States
AU: Eglinton, T I
EM: teglinton@whoi.edu
AF: Woods Hole Oceanographic Institute, MS#4, Woods Hole, MA 02543 United States
AB: Open savannah grasslands (dominated by C4 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 vegetation variability. 3 ka sampling resolution enables orbital-scale resolution of vegetation variability for short time windows spanning the last 9.4 Ma. DSDP Site 231 in the Gulf of Aden is well positioned to record northeast Africa vegetation change and is capable of extending reconstructions of environmental change beyond the time span of most lacustrine records. The biomarker data show large-amplitude vegetation variability as early as 3.8 Ma, prior to the onset of large amplitude northern hemisphere glacial interglacial cycles. Most C4 expansion occurs after 3.4 Ma. We sampled orbital-scale oscillations of up to 5 per mil, almost as large as the observed late Neogene range of 7 per mil, suggesting that large and repeated oscillations between more open and more closed landscapes were an important aspect of northeast African vegetation change during the last 4 Ma.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1055 Organic and biogenic geochemistry
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005