Unusual carbon isotope compositions of biomarker hydrocarbons in a Permian tasmanite

Journal Article · Wed Sep 01 00:00:00 EDT 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90316-O· OSTI ID:5168079

Simoneit, B R.T. ^[1]; Schoell, M; Dias, R F ^[2]; De Aquino Neto, F R ^[3]

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1. Oregon State Univ., Corvallis, OR (United States)
2. Chevron Petroleum Technology Co., La Habra, CA (United States)
3. Universidade Federal do Rio de Janeiro (Brazil)

The Permian oil shale sample of this study is from a deposit in Tasmania in which the only recognizable structures are large, thick-walled, unicellular specimens of the green algae Tasmanites. The fossils are so densely packed that this shale is termed tasmanite. The carbon isotopic composition of bulk kerogen carbon ([sigma]C[sup 13]C[sub org] = [minus]16.6[per thousand], vs. PDB) is unusually enriched in [sup 13]C compared to marine Permian organic carbon ([minus]25 to [minus]30[per thousand]). This [sup 13]C enrichment suggests specific environmental conditions (CO[sub 2] draw down) and/or physiological specialties (cell size and growth rate) of Tasmanites which, in modern environments, are known to cause [sup 13]C enrichment in marine phytoplankton. Isotope signatures of extractable organic species, unlike in normal immature oil shales, are considerably enriched in [sup 13]C compared to the kerogen. The isotopic similarity of all the cyclic terpanes in the sample, together with their occurrence in the free lipids and kerogen, suggests that they have a common origin and are biosynthesis products of the marine unicellular green algae Tasmanites. The tetracyclic terpanes, therefore, are not des-A-oleananes derived from land plants but are possibly monoaromatic des-A-gammaceranes or other des-A-triterpenoids derived from marine sources. The unusual enrichment in [sup 13]C in the cyclic hydrocarbons is hypothesized to result from the special growth conditions of the algae. Isoprenoids and n-alkanes are also likely biosynthesis products of Tasmanites, possibly during the spore formation stage when physiological and environmental conditions were different than during planktonic biosynthesis.

• OSTI ID: 5168079
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:17; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
54 ENVIRONMENTAL SCIENCES
HYDROCARBONS
ISOTOPE RATIO
OIL SHALES
CHEMICAL COMPOSITION
PALEOCLIMATOLOGY
PERMIAN PERIOD
ALGAE
ALKANES
BIOLOGICAL INDICATORS
CARBON 13
CARBON CYCLE
CLIMATIC CHANGE
FOSSILS
KEROGEN
TERPENES
BITUMINOUS MATERIALS
CARBON ISOTOPES
CARBONACEOUS MATERIALS
ENERGY SOURCES
EVEN-ODD NUCLEI
FOSSIL FUELS
FUELS
GEOLOGIC AGES
ISOTOPES
LIGHT NUCLEI
MATERIALS
MATTER
NUCLEI
ORGANIC COMPOUNDS
ORGANIC MATTER
PALEONTOLOGY
PALEOZOIC ERA
PLANTS
ROCKS
SEDIMENTARY ROCKS
SHALES
STABLE ISOTOPES
040500* - Oil Shales & Tar Sands- Properties & Composition
540210 - Environment
Terrestrial- Basic Studies- (1990-)