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dc.contributor.authorPedentchouk, N.
dc.contributor.authorFreeman, K.
dc.contributor.authorHarris, N.
dc.contributor.authorClifford, D.
dc.contributor.authorGrice, Kliti
dc.identifier.citationPedentchouk, Nikolai and Freeman, Katherine H. and Harris, Nicholas B. and Clifford, David J. and Grice, Kliti. 2004. Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins. Organic Geochemistry 35: pp. 33-45.

We conducted molecular biomarker and compound-specific carbon isotope analyses of off-line pyrolyzates from lacustrine samples recovered by ONEZ-1 well (the Kissenda Formation) in the Gabon Basin and Well A (the Maculungo Formation) in the Kwanza Basin in West Africa. Pyrolyzates from ONEZ-1 well contain isotopically depleted 1,2,3,4-tetramethylbenzene (1,2,3,4-TetraMB; 26.1 to 29.4%) and 1,2,4-trimethylbenzene (1,2,4-TriMB; 26.4 to 29.7%), which are isotopically similar to aryl isoprenoids (29.9 and 31.2%) and b-carotane (28.5 to 31.3%) identified in the bitumen fractions. Pyrolyzates from 3 samples in the lower sections of Well A contain isotopicallyenriched 1,2,3,4-TetraMB (ca. 16%) and 1,2,4-TriMB (ca. 14%), consistent with an origin from diagenetic products of isorenieratene/chlorobactene biosynthesized by green sulfur bacteria (Chlorobiaceae). Pyrolyzates from five samples in the upper sections of Well A are characterized by the presence of intermediate carbon-isotope values of 1,2,3,4- TetraMB (20.7 to 22.8%) and 1,2,4-TriMB (19.3 to 21.2%) and isotopically enriched isorenieratane (ca. 14.5%). Off-line pyrolyzates from these lacustrine source rocks represent two distinct end members: 13C-depleted diagenetic products of b-carotene derived from a lacustrine algal source and 13C-enriched diagenetic products of isorenieratene/chlorobactene derived from green sulfur bacteria. Organic matter (OM) from ONEZ-1 well shows a significant proportion of algal biomass with a 13C-depleted composition. The presence of 13C-enriched biomarkers derived from carotenoids of Chlorobiaceae from samples in the lower part of Well A indicates the development of photic zone euxinia and a significant biogeochemical role of sulfur. In the upper section of Well A, the 1,2,3,4-TetraMB and 1,2,4- TriMB have 13C values indicative of contributions from both Chlorobiaceae and algae to the OM.

dc.titleSources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins
dc.typeJournal Article
dcterms.source.titleOrganic Geochemistry

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Copyright © 2004 Elsevier B.V. All rights reserved

curtin.accessStatusFulltext not available
curtin.facultyDepartment of Applied Chemistry
curtin.facultySchool of Science and Computing
curtin.facultyFaculty of Science and Engineering

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