Normal fatty acids in sediments

Abstract

Normal fatty acids have been found by several investigators in a number of sediments ranging in age from Precambrian to Recent. This paper summarizes these occurrences. A variety of molec‐ular distributions have been observed. In most sediments, even‐carbon‐numbered normal fatty acids are much more abundant than those with odd carbon numbers; in some sediments, however, concentrations of even‐ and odd‐carbon‐numbered normal fatty acids are about equal. Normal fatty acids have been postulated as pos‐sible precursors for normal paraffin hydrocarbons in petroleum because of 1) structural similarities between the two kinds of molecules, 2) ubiquity of fatty acids in biological materials, 3) fatty acid‐normal paraffin relationships in sediments, and 4) distribution of normal paraffins in some crude oils. Evidence suggests that normal fatty acids may be precursors for many normal paraffins of intermediate and high molecular weights found in petroleum. Detailed mechanisms of chemical reactions by which normal paraffins can be de‐rived from fatty acids in sediments under geo‐logically reasonable conditions have yet to be defined.

Late Pleistocene changes in terrestrial biomarkers in sediments from the central Arctic Ocean

“…Although there is no unambiguous evidence for phytoplankton biomarkers, the presence of short-chain C 14 -C 18 n-fatty acids and cholesterol suggests some contribution of aquatic organisms (Kvenvolden et al, 1967;Huang and Meinschein, 1979). The abundance ratios of β-sitosterol to cholesterol and of long-chain to short-chain n-acids both exhibit a similar trend: relatively high values in MIS-6 (Figs.…”

“…The average CPI values of these compounds are generally high (3.7-4.9), and the distribution pattern is typical of terrestrial higher plant waxes (Eglinton and Hamilton, 1967;Kvenvolden et al, 1967). This pattern indicates that the OM was derived mainly from fresh higher plant material.…”

Abundant non-hydrocarbons in crude oils from the western Qaidam Basin, northwest China

“…It has been reported that the CPI values of n-fatty acids and n-alkanols are in the range of 3.2-13.8 and 11.5-34.2 in living plant leaf waxes, respectively (Rieley et al, 1991), and of 4.2-18.2 and 1.3-17.4 in recent marine sediments, respectively (Keswani et al, 1984). With the increasing thermal maturity, the molecular distribution of n-fatty acids and n-alkanols with a high CPI is presumed to be transformed into a distribution with a CPI value of approximately one (Kvenvolden, 1966(Kvenvolden, , 1967Jaffé and Gardinali, 1990). The similarity of the CPI values of nfatty acids and n-alkanols in the crude oils to those in living plant leaves and recent marine sediments, together with the presence of abundant unsaturated homologues and stenols, agrees with the low maturity of the crude oils.…”

Late Pleistocene variation in lignin and fatty acids from core TKN-2004 in a small mountain basin in central Japan

“…Although continuous samples. Short-chain C 14 -C 18 n-fatty acids (SFA) are derived mainly from aquatic organisms, whereas long-chain C 26 -C 30 n-fatty acids (LFA) are derived predominantly from vascular plants (Kvenvolden, 1967). Mid-chain C 20 -C 24 n-fatty acids (MFA) are abundant in submerged and floating freshwater aquatic macrophytes (Ficken et al, 2000).…”