Possible algal origin of long chain odd n-alkanes in immature sediments as revealed by distributions and carbon isotope ratios

Eric Lichtfouse (1) , Sylvie Derenne (2) , André A. Mariotti (2) , Claude Largeau (2)

1 ASD - Agronomy for Sustainable Development
2 Bioemco - Biogéochimie et écologie des milieux continentaux

A Pliocene oil shale (Pula, Hungary), a C3 plant Triticum aestivum and a C4 plant Zea mays were compared using isotopic composition of bulk organic matter, along with distributions and individual carbon isotope ratios of n-alkanes from organic extracts. The microalga Botryococcus braunii (A race) was thus shown to be the main source of the predominant 27, 29 and 31 n-alkanes of Pula sediment Therefore, the dominance of odd carbon-numbered n-alkanes in the range C25–35 in extracts from immature sediments shall not be systematically assigned to higher plant contribution but algal input is also possible. In fact, the long chain n-alkanes with an odd predominance previously observed in extracts of various immature sediments are likely to be derived at least partially, from algae.

Mots clés: carbon-13; n-alkane; n-alkene; Pula oil shale; Botryococcus braunii; alga; plant waxes sediment; 13C

Domaines: Chimie analytique; Géochimie

Eric Lichtfouse, Sylvie Derenne, André A. Mariotti, Claude Largeau. Possible algal origin of long chain odd n-alkanes in immature sediments as revealed by distributions and carbon isotope ratios. Organic Geochemistry, 1994, 22, pp.1023-1027. ⟨10.1016/0146-6380(94)90035-3⟩. ⟨hal-00175806⟩