Identification and origin of Δ 8(14)5α - and Δ 14 5α -sterenes and related hydrocarbons in an immature bitumen from the Monterey Formation, California
Abstract
The aliphatic hydrocarbon fraction of an immature Monterey bitumen contains a high relative abundance of C 27-C 29Δ 4, Δ 5, Δ 8(14) 5α - and Δ 14 5α -sterenes, each having a very similar carbon number distribution. This is the first report of abundant Δ 8(14) 5α - and Δ 14 5α - sterenes in an immature sediment. The Δ 4 and Δ 5 sterenes appear to originate directly from Δ 5 sterols. For the Δ 8(14) 5α - and Δ 14 5α sterenes we propose an origin from Δ 7 5α -sterols which may be derived from a microbial transformation of Δ 5 sterols. The presence of 5α- and 5β-steranes in an unusual ratio of ca. 55:45 suggests the formation of a high abundance of 5β-stanols via the known microbial reduction pathway of δ 5 sterols.
- Publication:
-
Geochimica et Cosmochimica Acta
- Pub Date:
- March 1992
- DOI:
- 10.1016/0016-7037(92)90058-Q
- Bibcode:
- 1992GeCoA..56.1223P