Radiocarbon Dating of Individual Fatty Acids as a Tool for Refining Antarctic Margin Sediment Chronologies

Abstract

ABSTRACT. We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C 14 , C 16 , and C 18 ) fatty acids isolated from Ross Sea surface sediments. The corresponding 14 C ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular 14 C variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular 14 C chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 14 C yr. The focus of this study is to determine the validity of compound-specific 14 C analysis as a technique for reconstructing chronologies of Antarctic margin sediments.

Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses

“…Polycyclic aromatic hydrocarbons (PAH) have been one of the subjects (Reddy et al 2002a,b;Mandalakis et al 2004;Gregory et al 2005;Zencak et al 2007). The origin of fatty acids in sediments has also been studied (Pearson et al 2001;Hwang and Druffel 2003;Ohkouchi et al 2003). Alkenones in sediments co-occurring with foraminifera were investigated by (Mollenhauer et al 2003(Mollenhauer et al , 2005a.…”

Spatial and temporal dynamics of biogeochemical processes in the Fraser River, Canada : a coupled organic-inorganic perspective

“…The radiocarbon composition of these fatty acids (Fig. 6) exhibits the commonly observed trend of older age with increasing chain length (Ohkouchi et al, 2003;Drenzek et al, 2007;Matsumoto et al, 2007).…”

“…The age of individual organic compounds offers insight to the cycling of distinct components of the bulk organic carbon pool Ohkouchi et al, 2003). In particular, the ages of vascular plant biomarkers such as long-chain fatty acids can also be used to assess the terrestrial residence time of biospheric organic carbon .…”

Transfer of organic carbon through marine water columns to sediments – insights from stable and radiocarbon isotopes of lipid biomarkers

“…AIOC-based chronology, however, is complicated by "contamination" by unknown amounts of relict OC (Sackett et al, 1974). To overcome this problem, Ohkouchi et al (2003) applied a compound-specific radiocarbon analysis of sedimentary fatty acids for cores from the Gentoo and Adelie sites and found a 1200-2000 year offset between the ages of fatty acids and AIOC. The fatty acid-derived sedimentation rate was 7.5 cm kyr −1 vs. an AIOC-derived rate of 15 cm kyr −1 .…”

“…Straight-chained hydrocarbons were separated from branched and cyclic hydrocarbons by urea adduction. Alkenones were isolated by sequential silica gel, AgNO 3 -silica gel chromatography and urea adduction after Ohkouchi et al (2005). Alcohols and sterols were acetylated with pyridine and acetic anhydride.…”