25th International Meeting on Organic Geochemistry IMOG 2011

P-469
Impact of anaerobic methane oxidizing archaea on TEXL86
paleotemperature records from Antarctica
Stefan Schouten 1 , Veronica Willmott 1 , Eugene Domack 2 , Rieneke Gieles 1 , Jaap
Sinninghe Damste 1
1 Royal Netherlands Institute for Sea Research, Den Burg, Texel, Netherlands, 2 Hamilton College, Clinton,
NY, United States of America (corresponding author:stefan.schouten@nioz.nl)
The TEX86 (TetraEther indeX of lipids with 86 carbon
atoms), is an organic paleothermometer based on the
relative distribution of glycerol dibiphytanyl glycerol
tetraether lipids (GDGTs) biosynthesized by marine
Thaumarchaeota, one of the dominant prokaryotes of
today‘s oceans. Mesocosm studies show that this
ratio increases with increasing temperatures and core
top studies have shown that TEX86 correlates well
with annual mean sea surface temperatures.
Recently, a revised index, the TEX L 86, was proposed
to reconstruct temperatures in polar area‘s [1]. The
use of TEX L 86 in polar areas is potentially promising
because it can be measured in carbonate poor
sediments and is unlikely to be influenced by soil
input in this region.
Here we generated a TEX L 86 temperature
record in a Holocene, 20 m long sediment core from
the Western Antarctic Peninsula. The TEX L 86 derived
temperature (Fig. 1) of the upper section of the core,
between 0 and 6.5 mbsf, oscillates slightly between 0
and 2°C, consistent with the annual temperature
fluctuation of Antarctic Surface Water (AASW) in the
Western Antarctic Peninsula. However, below 6 m
core depth, the calculated temperatures increase to
values up to 25°C, which is entirely inconsistent with
the climate development in this geographical location
during the Holocene period. The data clearly show
that the proxy is not working in this section of the core
and is severely biased. Since the extreme high
TEX L 86 temperatures also cannot be caused by a bias
in seasonality or depth habitat of the
Thaumarchaeota, the likely cause must be an input of
GDGTs not derived from the pelagic water column.
An input of soil GDGTs can be excluded as the BIT
index, a proxy for the input of soil derived GDGTs,
were always