The diagenetic fate of taraxer-14-ene and oleanene isomers

Journal Article · Sat Oct 01 04:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(88)90312-2· OSTI ID:5342402

Ten Haven, H L; Rullkoetter, J ^[1]

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1. Institute of Petroleum and Organic Geochemistry, Juelich (West Germany)

The extractable organic matter in Holocene to early Miocene deep-sea sediments from Site 645 (ODP Leg 105) in Baffin Bay contains almost exclusively biological markers of terrigenous origin. Pentacyclic triterpenoids of the {alpha}-(ursene) and {beta}-amyrin (oleanene) type often occur as the most abundant compounds in the aliphatic hydrocarbon, ketone and alcohol fractions of the sediment extract. A specific diagenetic reaction involves the conversion of taraxer-14-ene into olean-12-ene in the upper 700 meters of the sedimentary sequence. The taraxerene-to-oleanene conversion is complete before the onset of isomerization of diasterenes at C-20. In the sediment as well as in laboratory simulation experiments, olean-12-ene further isomerizes to olean-13(18)-ene and olean-18-ene, the latter of which may be the direct precursor of 18{beta}(H)- and 18{alpha}(H)-oleanane found in sediments containing more mature organic matter and in crude oils. The subsurface interconversion of these triterpenoid skeletons indicate that oleanane does not necessarily start life as an oleanoid.

• OSTI ID: 5342402
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 52:10; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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