Alkane and hydrocarbon concentrations of ODP Leg 104 sites

Sedimentary extractable organic matter was analyzed at three ODP Leg 104 sites in the Norwegian Sea. Organic carbon content ranged from less than 0.1% to a maximum of 1.8%. Extractable organic matter content and unresolved complex mixture concentrations were low and randomly distributed. Low levels of aliphatic (branched and normal) and aromatic hydrocarbons were detected in all of the sediments analyzed. Total aliphatic and aromatic hydrocarbon concentrations ranged from 176 to 3,214 and 6 to 820 ppb, respectively. The concentrations of individual aliphatic (n-C15 to n-C32) and aromatic (two- to five-ring) hydrocarbons were generally less than 50 ppb and less than 10 ppb, respectively. No significant trend with sub-bottom depth was observed in either bulk organic matter or individual hydrocarbon concentrations. The predominant source of Cenozoic sedimentary hydrocarbons is concluded to be ice-rafted debris from the adjacent continent. All sites contain a mixture of recycled, mature petroleum-related and terrestrially derived hydrocarbons.

Polyaromatic hydrocarbons in sediments from the Barents and White Seas

Polycyclic aromatic hydrocarbons (PAHs) are common environmental contaminants which can be derived from anthropogenic sources, such as combustion and discharges from extraction and transport, and natural processes, including leakage and erosion of fossil carbon. Natural PAH sources contribute, along with biological activities and terrestrial run-off, to the organic carbon content in sediments.The Barents Sea region is far from many anthropogenic sources of PAH, but production and trans-shipment of hydrocarbons is increasing. We present data for polycyclic aromatic hydrocarbon (PAH) concentrations in bottom sediments from 510 stations in the Barents and White Seas, and along the northern coast of Norway.

(Table 1) Organic geochemistry at DSDP Leg 71 Holes

Forty-three core samples from Sites 511 through 514 of DSDP Leg 71 were analyzed geochemically. The black shales at the bottom of Hole 511, in the basin province of the Falkland Plateau, contain an average of 1590 ppm extractable organic matter (EOM) and 120 ppm hydrocarbons. Whereas molecular type-carbon number distributions of mono- and polynuclear aromatic hydrocarbons and their sulphur and oxygen analogues in the black shale "aromatic hydrocarbon" fractions are very similar to those of many crude oils, other data - gas chromatography (GC) fingerprint, pyrolysis GC, visual kerogen analysis, H/C ratio - suggest the black shale section is thermally immature. Together, these observations imply that many of the hydrocarbons were deposited with the original sediments or are diagenetic products of other biological compounds. Pyrograms of the humic acid and kerogen fractions from the black shale interval are typical of geopolymers derived from marine algal material. It appears that these humic acids and kerogens are derived from the same lipid stock.

(Table) Content of organic compounds in the bottom sediments of the Volga River estuary

Materials from different spheres of the Earth are ultimately delivered to bottom sediments, which serve as a natural recorder of the functioning of other spheres and originate as a result of the accumulation of their substances. Sedimentary material and species of river-transported elements are subjected to dramatic reworking in marginal filters, where river and sea waters are mixed. These processes are most important for the Caspian Sea, where runoffs of rivers (especially the Volga River) and the intense development and transportation of hydrocarbon fuel by tankers and pipelines (related to the coastal petroleum industry in the Sumgait and Baku ports, Apsheron Peninsula) are potential sources of hydrocarbon pollution. Previously obtained data showed that the total content of hydrocarbon fraction (i.e., the sum of aliphatic hydrocarbons (AHC) and polycyclic aromatic hydrocarbons (PAH)) in bottom sediments varied within 29-1820 µg/g. The content of petroleum hydrocarbons in the northeastern Caspian region varied from 0.052 to 34.09 µg/g with the maximum content in the Tengiz field. The content of six polyarenes in the Volga delta sediments was no more than 40 ng/g. To determine the recent HC pollution of bottom sediments and trends in the functioning of the Volga marginal filter, in summer of 2003 and 2004 we analyzed bottom sediments (58 samples) in the river waterway; Kirovsk channel; Bakhtemir and Ikryanoe branches; tributaries of the Kizan, Chagan, and other rivers; and the Caspian seashore.

Geochemistry and pyrolysis at DSDP Hole 77-535

There are substantial differences in the character of organic matter contained in the Pleistocene and Cretaceous sedimentary sequences of DSDP Site 535. The argillaceous Pleistocene section contains type III, gas-prone organic matter whereas the calcareous Cretaceous section is dominated by type II, oil-prone organic matter. A more detailed investigation of the Cretaceous section reveals that the finely laminated limestones of Valanginian to Barremian age are of good to excellent source quality. The indigenous organic matter contained within this organically rich section is thermally immature, not having undergone sufficient thermal diagenesis for the generation and expulsion of hydrocarbons. Within this stratigraphic section, however, staining by mature hydrocarbons was detected. These stains are associated with a fractured interval. These fractures may in turn represent potential migration pathways.

Organic geochemistry of ODP Leg 135 sediment samples

The average total organic carbon (TOC) content obtained after Rock-Eval/TOC analysis of 156 sediment samples from the eight sites cored during Leg 135 is 0.05%. Hence, the TOC content of Leg 135 sediments is extremely low. The organic matter that is present in these samples is probably mostly reworked and oxidized material. Ten sediment samples were selected for extraction and analysis by gas chromatography and gas chromatography-mass spectrometry. Very low amounts of extractable hydrocarbons were obtained and some aspects of the biomarker distributions suggest that these hydrocarbons are not representative of the organic matter indigenous to the samples. A sample of an oil seep from Pili, Tongatapu was also analyzed. The seep is a biodegraded, mature oil that shows many characteristics in common with previously published analyses of oil seeps from Tongatapu. Biomarker evidence indicates that its source is a mature, marine carbonate of probable Late Cretaceous-Early Tertiary age. The source rock responsible for the Tongatapu oil seeps remains unknown.

Composition of swamp waters from the lower Tom' River Basin

New data on chemical and trace component compositions of acidic and low acidic swamp waters and other types of low mineralized waters are reported in the paper. Special attention is paid to dissolved organic compounds: fulvic and humic acids, bitumen, and hydrocarbons. For the first time detailed data on organic trace components (alkanes, pentacyclic terpenoids, steranes, alkylbenzenes, naphthalenes, phenanthrenes, tetraarenes, etc.) in the swamp waters of the Western Siberia: are reported.

Hydrocarbons, sterols and alkenones at time series station KERFIX

Hydrocarbons, sterols and alkenones were analyzed in samples collected from a 10 month sediment trap time series deployed in the Indian Ocean sector of the Southern Ocean. Fluxes and within-class distributions varied seasonally. During higher mass and organic carbon (OC) flux periods, which occurred in austral summer and fall, fresh marine inputs were predominant. Vertical fluxes were most intense in January, but limited to one week in duration. They were, however, low compared with other oceanic regions. In contrast, low mass and OC flux periods were characterized by a strong unresolved complex mixture (UCM) in the hydrocarbon fraction and a high proportion of stanols as a result of zooplanktonic grazing. Terrigenous inputs were not detectable. The alkenone compositions were consistent with previous data on suspended particles from Antarctic waters. However, UK'37 values diverged from the linear and exponential fits established by Sikes et al. (1997, doi:10.1016/S0016-7037(97)00017-3) in the low temperature range. The seasonal pattern of alkenone production implied that IPT (integrated production temperature) is likely to be strongly imprinted by austral summer and fall SST (sea surface temperature).

Lithology, stage, organic carbon, d13C, hydrocarbons and fatty acids at DSDP Hole 93-603B

Organic-matter-rich Upper Cretaceous claystones from DSDP Hole 603B, lower continental rise, had organic carbon values ranging from 1.7 to 13.7%, C/N ratios from 32 to 72, and d13C values from -23.5 to -27.1 per mil. Lipid class maxima for the unbound alkanes (C29 and C31), unbound fatty acids (C28 and C30), and bound fatty acids (C24, C26 , and C28) and the strong odd-carbon and even-carbon preferences, respectively, suggested that the organic matter in these sediments was partially the result of input from continental plant waxes. Transport of the organic-matter-rich sediments to the deep sea from the near-shore environment probably resulted from turbiditic flow under oxygen-stressed conditions.

Organic geochemistry of sediments at DSDP Legs 56-57 Holes

The quantity, type, and maturity of the organic matter of Quaternary and Tertiary sediments from the Japan Trench (DSDP Leg 56, Sites 434 and 436; and Leg 57, Sites 438, 439 and 440) were determined. The hydrocarbons in lipid extracts were analyzed by capillary- column gas chromatography and combined gas chromatography/ mass spectrometry. Kerogen concentrates were investigated by microscopy, and vitrinite-reflectance values were determined. Measured organic-carbon values were in the range of 0.13 to 1.00 per cent. Extract yields, however, were extremely low. Normalized to organic carbon, total extracts ranged from 4.1 to 15.7 mg/g Corg. Gas chromatography of non-aromatic hydrocarbons showed that all sediments, except one Oligocene sample, contained very immature, mainly terrigenous organic material. This was indicated by n-alkane maxima at C29 and C31 and high odd-carbon-number predominances. Unsaturated steroid hydrocarbons were found to be major cyclic compounds in lower- and middle-Miocene samples from the upper inner trench slope (Sites 438 and 439). Perylene was the dominating aromatic hydrocarbon in all but the Oligocene sample. Microscopy showed kerogens rich in terrigenous organic particles, with a major portion of recycled vitrinite. Nevertheless, almost all the liptinite particles appeared to be primary. This is a paradox, as the bulk of the samples were composed of hemipelagic mineral matter with a major siliceous biogenic (planktonic) component. A trend of reduced size and increased roundness can be seen for the vitrinite/ inertinite particles from west to east (from upper inner trench slope to outer trench slope). All sediments but one are relatively immature, with mean huminite-reflectance values (Ro)in the range of 0.30 to 0.45 per cent. The oldest and deepest sediment investigated, an Oligocene sandstone from Site 439, yielded a mean vitrinitereflectance value of 0.74 per cent and a mature n-alkane distribution. This sample may indicate a geothermal event in late Oligocene time. It failed to affect the overlying lower Miocene and may have been caused by an intrusion. Boulders of acidic igneous rocks in the Oligocene can be interpreted as witnesses of nearby volcanic activity accompanied by intrusions.