Structural identification of steryl alkyl ethers in marine sediments

Abstract

Steryl alkyl ethers have been reported to occur in immature marine sediments up to Cretaceous age. Here, we report their unambiguous structural identification in Holocene sediments from the Arabian Sea, Pleistocene sediments from the southeast Atlantic and a Miocene sediment from the Monterey formation through chemical degradation experiments and synthesis. We show that the main steryl alkyl ethers in sediments from the southeast Atlantic are cholest-5-enyl 3b-(2-dodecanyl) ether and cholest-5-enyl 3b-(3-dodecanyl) ether together with their 24-methyl and 24-ethyl pseudo-homologues. Steryl alkyl ethers in sediments from the Arabian Sea are dominated by cholest-5-enyl 3b-(5-decanyl) ether and cholest-5-enyl 3b-(4-decanyl) ether together with their 24-methyl and 24-ethyl pseudo-homologues. The structures suggest that these compounds are formed by direct biosynthesis by as yet unknown marine organisms.

Systematic pattern in – Temperature residuals for surface sediments from high latitude and other oceanographic settings

“…Alkenone content and, in particular, compositional attributes such as the unsaturation index U K 0 37 (Brassell et al, 1986) could not be quantified reliably due to the abundant presence of a C 27 , C 28 and C 29 steryl -alkyl ether series like that previously described by Schouten et al (2005). Evaluation of GCmass fragmentograms for m/z 369, 381 and 383 indicated that interference with the di-unsaturated alkenone, K37:2m, was due primarily to a component of the C 27:1 steryl -alkyl series (m/z 369) and that interference with the triunsaturated alkenone, K37:3m, was due to components of both the C 28:1 (m/z 383) and a C 28:2 (m/z 381) steryl -alkyl series.…”