古環境を復元する指標としてのバイオマーカー-太平洋における深海底堆積物を例として- Biomarkers as Tools for Reconstructiong Paleoenvironments
We present analytical results of organic compounds in the deep sea sediments recovered from the Central Pacific and the western tropical Pacific and describe recent progresses in sedimentary biomolecules as tools for reconstructing paleoenviroments. Biomolecules derived from terrestrial higher plants such as C<SUB>25</SUB>-C<SUB>35</SUB> <I>n</I>-alkanes, C<SUB>24</SUB>-C<SUB>28</SUB> fatty alcohols, or C<SUB>23</SUB>-C<SUB>34</SUB> fatty acids in the surface sediments from 175° E transect show high concentrations in the higher latitudes in the Northern Hemisphere. Relative abundances of these terrestrial biomarkers are markedly different between low (15°N-15°S) and high (48°N-19°N) latitudes. Such a difference could be interpreted in terms of different wind regimes between the two areas. Unsaturation degree of long-chain alkenones (U<SUP>k</SUP><SUB>37</SUB>) derived from haptophyte algae suggests that sea surface temperature in the western tropical Pacific during the last glacial maximum was nearly the same as that of the present. We also found that the alkenone abundances over the last 20 kyr are anti-correlated with sedimentary nitrogen isotopic ratios, suggesting that a production rate of alkenones by haptophyte algae is controlled by the nutritional state of the algae.