Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins
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 co...
| Main Authors: | , , , , |
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| Format: | Journal Article |
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Elsevier
2004
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| Online Access: | http://hdl.handle.net/20.500.11937/25121 |
| _version_ | 1848751619667132416 |
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| author | Pedentchouk, N. Freeman, K. Harris, N. Clifford, D. Grice, Kliti |
| author_facet | Pedentchouk, N. Freeman, K. Harris, N. Clifford, D. Grice, Kliti |
| author_sort | Pedentchouk, N. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T07:55:37Z |
| format | Journal Article |
| id | curtin-20.500.11937-25121 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T07:55:37Z |
| publishDate | 2004 |
| publisher | Elsevier |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-251212017-09-13T16:07:21Z Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins Pedentchouk, N. Freeman, K. Harris, N. Clifford, D. Grice, Kliti 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. 2004 Journal Article http://hdl.handle.net/20.500.11937/25121 10.1016/j.orggeochem.2003.04.001 Elsevier restricted |
| spellingShingle | Pedentchouk, N. Freeman, K. Harris, N. Clifford, D. Grice, Kliti Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title | Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title_full | Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title_fullStr | Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title_full_unstemmed | Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title_short | Sources of alkylbenzenes in Lower Cretaceous lacustrine source rocks, West African rift basins |
| title_sort | sources of alkylbenzenes in lower cretaceous lacustrine source rocks, west african rift basins |
| url | http://hdl.handle.net/20.500.11937/25121 |