25th International Meeting on Organic Geochemistry IMOG 2011

P-488
Paleoenvironmental changes from organic matter composition
in the California margin sediments (ODP Leg 167, Hole1017E)
during the last 45kyrs
Shuichi Yamamoto 1 , Chieko Dairiki 1 , Ryoshi Ishiwatari 2
1 Soka University, Tokyo, Japan, 2 Tokyo Metropolitan University, Tokyo, Japan (corresponding
author:syama@soka.ac.jp)
Climate instability during the last glacial period
which correspond to Dansgaard-Oeshger (D-O)
events has already been recognized in the California
margin of the northeast Pacific from investigations of
18 O in foraminifera and sea surface temperature
(SST) by alkenone [1][2]. However, it is still important
to clarify how the marine and land ecosystems
responded to climate changes during the last glacial
period.
The sediment samples for our study were obtained
from ODP Hole 1017E located on the Santa Lucia
slope (34°32.10‘ N, 121°06.43‘ W). Eighty two organic
compounds such as fatty acids, alcohols, lignin
phenols, cutin acids and sterols in the sediment
during the last 45 kyrs were analyzed by
thermochemolysis with tetramethyl ammonium
hydroxide and GC-MS.
The vertical distribution of the total amount of
organic compounds identified is synchronized to total
organic carbon (Fig. 1 (a)) and SST (Fig. 1(g) as
shown in Fig. 1(b) with high concentration during the
periods of interglacial and interstadial warming during
the Holocene, Bølling/Allerød and D-O events. The
vertical profiles of proportions of marine derived (e.g.,
phytol, n-C14-C18 fatty acids, almost sterols), land
derived (e.g., lignin phenols, n-C28-C32 fatty acids,
cutin acids) and the other organic compounds show
that the percentages of marine origin and land origin
correspond well to the SST (Fig. 1(c) and (d)); the
proportion of marine origin is high (64.2 %) during
Holocene and low (49.4 %) during Younger Dryas to
marine isotope stage 3, while those of land origin is
low (15.8 %) and high (31.0 %), respectively. Results
from factor analysis to the vertical profiles of organic
compounds indicates that the first and second factor
loadings also correlate well to the SST (r 2 =0.724,
r 2 =0.736, Fig. 1(e) and (f)). Then, the results suggest
that contribution to sedimentary organic matter from
marine and land depend on temperature.
[1] Kennett et al. (2000) Proc. Ocean Drill. Program
Sci. Results, 167, 249.
[2] Seki et al. (2002) Geophysical Research Letters,
29, 1.
612