Organic compounds in surface sediments from the Pakistan continental margin
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| Format: | Dataset Open Access |
| Sprache: | en |
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2000
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| author | Schulte, Sonja Mangelsdorf, Kai Rullkötter, Jürgen |
| author_facet | Schulte, Sonja Mangelsdorf, Kai Rullkötter, Jürgen |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | In order to assess whether the oxygen-minimum zone (OMZ) in the Arabian sea has an effect on the preservation and composition of organic matter in surface sediments we investigated samples from three different transects on the Pakistan continental margin across the OMZ. In addition to determining the total amount of organic carbon (TOC), we analyzed the extractable lipids by gas chromatography, combined gas chromatography/mass spectrometry, and compound-specific stable carbon isotope measurements. The extractable lipids are dominated by marine organic matter as indicated by the abundance of lipids typical of marine biota and by the bulk and molecular isotopic composition. Sediments from within the OMZ are enriched in organic carbon and in several extractable lipids (i.e. phytol, n-alcohols, total sterols, n-C35 alkane) relative to stations above and below this zone. Other lipid concentrations, such as those of total n-fatty acids and total n-alkanes fail to show any relation to the OMZ. Only a weak correlation of TOC with mineral surface area was found in sediments deposited within the OMZ. In contrast, sediments from outside the OMZ do not show any relationship between TOC and surface area. Among the extractable lipids, only the n-alkane concentration is highly correlated with surface area in sediments from the Hab and Makran transects. In sediments from outside the OMZ, the phytol and sterol concentrations are also weakly correlated with mineral surface area. The depositional environment of the Indus Fan offers the best conditions for an enhanced preservation of organic matter. The OMZ, together with the undisturbed sedimentation at moderate rates, seems to be mainly responsible for the high TOC values in this area. Overall, the type of organic matter and its lability toward oxic degradation, the mineral surface area, the mineral composition, and possibly the secondary productivity by (sedimentary) bacteria also appear to have an influence on organic matter accumulation and composition. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_57049 |
| institution | PANGAEA |
| language | en |
| publishDate | 2000 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Organic compounds in surface sediments from the Pakistan continental margin Schulte, Sonja Mangelsdorf, Kai Rullkötter, Jürgen 3,7,11 Methyl, 15, Dimethyl, pentan-2dien-1ol, Phytol normalized to TOC, per unit mass total organic carbon; 4alpha,23,24-Trimethyl-5alpha-cholest-22E-en-3beta-ol, per unit mass total organic carbon; Arabian Sea; BCR; Box corer (Reineck); Calculated; Carbon, organic, total; Carbon in carbonate; DEPTH, sediment/rock; Element analyser CHN; Elevation of event; Event label; Gas chromatography; Gas chromatography - Mass spectrometry (GC-MS); iso-, antiso C15 and C17 acid, per unit mass total organic carbon; Latitude of event; Longitude of event; n-Alcohol, per unit mass total organic carbon; n-alkanes, total, per unit sediment mass; n-Hentriacontane normalized to total organic carbon; n-Pentatriacontane (C35H72), per unit mass total organic carbon; PAKOMIN; SO90; SO90_103KG; SO90_107KG; SO90_110KG; SO90_113KG; SO90_115KG; SO90_120KG; SO90_124KG; SO90_129KG; SO90_12KG; SO90_142KG; SO90_163KG; SO90_164KG; SO90_168KG; SO90_173KG; SO90_180KG; SO90_18KG; SO90_1KG; SO90_20KG; SO90_23KG; SO90_24KG; SO90_28KG; SO90_34KG; SO90_39KG; SO90_65KG; SO90_69KG; SO90_79KG; SO90_85KG; SO90_87KG; SO90_95KG; SO90_96KG; SO90_99KG; Sonne; Sum n-Tetracosanoic acid+n-Hexacosanoic acid per unit mass total organic carbo; sum per unit mass fatty acids (C12...C33) of total organic carbon; Sum sterols normalized to total organic carbon mass In order to assess whether the oxygen-minimum zone (OMZ) in the Arabian sea has an effect on the preservation and composition of organic matter in surface sediments we investigated samples from three different transects on the Pakistan continental margin across the OMZ. In addition to determining the total amount of organic carbon (TOC), we analyzed the extractable lipids by gas chromatography, combined gas chromatography/mass spectrometry, and compound-specific stable carbon isotope measurements. The extractable lipids are dominated by marine organic matter as indicated by the abundance of lipids typical of marine biota and by the bulk and molecular isotopic composition. Sediments from within the OMZ are enriched in organic carbon and in several extractable lipids (i.e. phytol, n-alcohols, total sterols, n-C35 alkane) relative to stations above and below this zone. Other lipid concentrations, such as those of total n-fatty acids and total n-alkanes fail to show any relation to the OMZ. Only a weak correlation of TOC with mineral surface area was found in sediments deposited within the OMZ. In contrast, sediments from outside the OMZ do not show any relationship between TOC and surface area. Among the extractable lipids, only the n-alkane concentration is highly correlated with surface area in sediments from the Hab and Makran transects. In sediments from outside the OMZ, the phytol and sterol concentrations are also weakly correlated with mineral surface area. The depositional environment of the Indus Fan offers the best conditions for an enhanced preservation of organic matter. The OMZ, together with the undisturbed sedimentation at moderate rates, seems to be mainly responsible for the high TOC values in this area. Overall, the type of organic matter and its lability toward oxic degradation, the mineral surface area, the mineral composition, and possibly the secondary productivity by (sedimentary) bacteria also appear to have an influence on organic matter accumulation and composition. |
| title | Organic compounds in surface sediments from the Pakistan continental margin |
| topic | 3,7,11 Methyl, 15, Dimethyl, pentan-2dien-1ol, Phytol normalized to TOC, per unit mass total organic carbon; 4alpha,23,24-Trimethyl-5alpha-cholest-22E-en-3beta-ol, per unit mass total organic carbon; Arabian Sea; BCR; Box corer (Reineck); Calculated; Carbon, organic, total; Carbon in carbonate; DEPTH, sediment/rock; Element analyser CHN; Elevation of event; Event label; Gas chromatography; Gas chromatography - Mass spectrometry (GC-MS); iso-, antiso C15 and C17 acid, per unit mass total organic carbon; Latitude of event; Longitude of event; n-Alcohol, per unit mass total organic carbon; n-alkanes, total, per unit sediment mass; n-Hentriacontane normalized to total organic carbon; n-Pentatriacontane (C35H72), per unit mass total organic carbon; PAKOMIN; SO90; SO90_103KG; SO90_107KG; SO90_110KG; SO90_113KG; SO90_115KG; SO90_120KG; SO90_124KG; SO90_129KG; SO90_12KG; SO90_142KG; SO90_163KG; SO90_164KG; SO90_168KG; SO90_173KG; SO90_180KG; SO90_18KG; SO90_1KG; SO90_20KG; SO90_23KG; SO90_24KG; SO90_28KG; SO90_34KG; SO90_39KG; SO90_65KG; SO90_69KG; SO90_79KG; SO90_85KG; SO90_87KG; SO90_95KG; SO90_96KG; SO90_99KG; Sonne; Sum n-Tetracosanoic acid+n-Hexacosanoic acid per unit mass total organic carbo; sum per unit mass fatty acids (C12...C33) of total organic carbon; Sum sterols normalized to total organic carbon mass |
| url | https://doi.org/10.1594/PANGAEA.57049 |