[B-PT02] Biomineralization and Geochemistry of Proxies

[BPT02-P02] New technique for extremely low quantity of alkenones: For extraction of high resolution record of secular environmental fluctuation.

*Takashi Hasegawa¹ (1.Faculty of Geoscience and Engineering, Institute of Science and Engineering, Kanazawa University)

Keywords:alkenone, paleotemperature, low quantitiy

Alkenones are strait-chain alkylketones with 37-42 carbon atoms synthesized by haptophyte algae. C37 alkenones with two or three unsaturation sites (C_37:2Me and C_37:3Me) are often employed for paleothermometry. For this proxy, a parameter, U^K’₃₇, is calculated from relative abundances of these two molecules obtained with gas-chromatography (GC). Alkenone paleothemometry has been a significant technique for Quaternary paleoceanography from marine deep sea cores while it has hardly been applied for samples lean in alkenones because of the instrumental limitation of GC. The purpose of this study is to develop a new technique of quantitative analysis for extremely minuscule quantity (<1% of conventional technique) of alkenones. It largely extends applicability of alkenone paleothermometry for Neogene, Paleogene, even Cretaceous sediments as well as for finely laminated lake sediments that potentially provide yearly climatic records from various regions of the world. As gas-chromatography/mass-spectrometry (GCMS) is a destructive technique, it has been thought to be unsuitable for quantitative analysis and to evaluate relative abundances of different molecules, despite its high sensitivity detector. However, it could be possible if we just focus on selected alkenones using appropriate standard materials. Test-and-error based investigation on two different polarity columns with different length in tandem and different ionization techniques (CI and EI) on GCMS will elucidate the best condition for sub-pico mol order quantification of alkenones on GCMS.