25th International Meeting on Organic Geochemistry IMOG 2011

P-493
Vegetation and soil organic matter input offshore southeastern
Australia based on organic proxies
Raquel Lopes dos Santos 1 , Daniel Wilkins 2 , Patrick De Deckker 2 , Stefan Schouten 1
1 Royal Netherlands Institute for Sea Research (NIOZ), Texel, Netherlands, 2 The Australian National
University (ANU), Canberra, Australia (corresponding author:raquel.santos@nioz.nl)
The Murray-Darling Basin (MDB) is the
largest river basin of Australia. The river and its
tributaries drain 1/7 th of the Australian continent and
had changed its course and outflow intensively over
the last 600 kyrs. Yet, not much is known about
changes in the vegetation of the basin and its outflow
during the last 2 glacial-interglacial cycles.
Here, we evaluate soil organic matter input
from the Murray-Darling river system to offshore
southeastern Australia (SEA) for the last ~135 kyrs
measuring the Branched and Isoprenoid Tetraether
(BIT) index. This index is based on a ratio between
branched GDGTs produced by soil bacteria and
crenarchaeol, a compound mainly produced by
marine Achaea. Additionally, we evaluate the
vegetation input by analyzing concentrations and
isotopic compostion of long chain n-alkanes. Odd long
chain n-alkanes are mainly derived from terrestrial
plants and their isotopic composition depends on the
isotopic composition of the atmospheric CO2,
physiological responses to environmental changes
and plant-types. Thus, we measured the carbon
isotopic composition of the long chain n-alkanes to
reconstruct vegetation changes during the wet and
dry phases of Australia. Sea surface temperature
offshore SEA was estimated using U K‘ 37 index.
BIT index was always very low (