Hydrocarbon biomarkers, thermal maturity, and depositional setting of tasmanite oil shales from Tasmania, Australia

Journal Article · Thu Sep 01 00:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90365-4· OSTI ID:6593605

Revill, A T; Volkman, J K; O'Leary, T ^[1]; Summons, R E; Boreham, C J ^[2]; Banks, M R; Denwer, K ^[3]

---

1. CSIRO Division of Oceanography, Tasmania (Australia)
2. Australian Geological Survey Organisation, Canberra (Australia)
3. Univ. of Tasmania (Australia)

This study represents the first geological and organic geochemical investigation of samples of tasmanite oil shale representing different thermal maturities from three separate locations in Tasmania, Australia. The most abundant aliphatic hydrocarbon in the immature oil shale from Latrobe is a C[sub 19] tricyclic alkane, whereas in the more mature samples from Oonah and Douglas River low molecular weight n-alkanes dominate the extractable hydrocarbon distribution. The aromatic hydrocarbons are predominantly derivatives of tricyclic compounds, with 1,2,8-trimethylphenanthrene increasing in relative abundance with increasing maturity. Geological and geochemical evidence suggests that the sediments were deposited in a marine environment of high latitude with associated cold waters and seasonal sea-ice. It is proposed that the organism contributing the bulk of the kerogen, Tasmanites, occupied an environmental niche similar to that of modern sea-ice diatoms and that bloom conditions coupled with physical isolation from atmospheric CO[sub 2] led to the distinctive [open quotes]isotopically heavy[close quotes] [delta][sup 13]C values for the kerogen. [delta][sup 13]C data from modern sea-ice diatoms supports this hypothesis. Isotopic analysis of n-alkanes in the bitumen suggests a multiple source from bacteria and algae. On the other hand, the n-alkanes generated from closed-system pyrolysis of the kerogen are mainly derived from the preserved Tasmanites biopolymer algaenan. The tricyclic compounds (mean -8[per thousand]) both in the bitumen and pyrolysate, have a common precursor. They are consistently enriched in [sup 13]C compared with the kerogen and probably have a different source from the n-alkanes. The identification of a location where the maturity of the tasmanite oil shale approaches the [open quotes]oil window[close quotes] raises the possibility that it may be a viable petroleum source rock.

• OSTI ID: 6593605
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 58:18; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
OIL SHALES
CHEMICAL COMPOSITION
MATURATION
BIOLOGICAL MARKERS
CARBON 13
EXPLORATION
GEOLOGIC HISTORY
ISOTOPE RATIO
PETROLEUM
BITUMINOUS MATERIALS
CARBON ISOTOPES
CARBONACEOUS MATERIALS
ENERGY SOURCES
EVEN-ODD NUCLEI
FOSSIL FUELS
FUELS
ISOTOPES
LIGHT NUCLEI
MATERIALS
NUCLEI
ROCKS
SEDIMENTARY ROCKS
SHALES
STABLE ISOTOPES
040200* - Oil Shales & Tar Sands- Reserves
Geology
& Exploration