Organic- and carbonate-carbon values and extract data for DSDP Holes 63-467 and 63-471

Quantity, type, and maturity of the organic matter of middle Miocene to Quaternary sediments from the eastern North Pacific (Deep Sea Drilling Project Leg 63) were determined. Hydrocarbons and fatty acids in lipid extracts were analyzed by capillary column gas chromatography and combined gas chromatography/mass spectrometry. Kerogens were investigated by Rock-Eval pyrolysis and microscopy, and vitrinite reflectance values were determined. At Site 467, in the San Miguel Gap of the outer California Continental Borderland, organic carbon contents range from 1.46% to 5.40%. Normalized to organic carbon, total extracts increase from about 10 to 36 mg/g Corg with depth. The organic matter is a mixture of both marine and terrestrial origin, with the marine organic matter representing a high proportion in some of the samples. Steroid hydrocarbons - sterenes and steradienes in the upper part of the section and steranes in the deepest sample - are the most abundant compounds in the nonaromatic hydrocarbon fractions. Perylene, alkylated thiophenes, and aromatic steroid hydrocarbons dominate in the aromatic hydrocarbon fractions of the shallower samples; increasing maturation is indicated by a more petroleumlike aromatic hydrocarbon distribution. Microscopy revealed a high amount of liptinitic organic matter and confirmed the maturation trend as observed from analysis of the extracts. The vitrinite reflectance may be extrapolated to a bottom-hole value of nearly 0.5% Ro. The liquid hydrocarbon potential of the sediments at higher maturity levels is rated to be good to excellent. At Site 471, off Baja California, organic carbon values are between 0.70% and 1.12%. Extract values increase with depth, as at Site 467. The investigation of the soluble and insoluble organic matter, despite some compositional similarities, consistently revealed a more terrigenous influx compared with Site 467. Thus the potential for liquid hydrocarbon generation is lower, the organic matter being more gas-prone. The deepest sample analyzed indicates the onset of hydrocarbon generation. At this site, frequent sand intercalations offer pathways for migration and possibly reservoir formation.

Carbonate, organic carbon and nitrogen, bitumen and rock-eval pyrolysis at DSDP Leg 79 Holes

The lipids and kerogens of 15 sediment samples from Site 547 (ranging from Pleistocene to Early Jurassic/Triassic) and 4 from Site 545 (Cretaceous) have been analyzed. A strong terrestrial contribution of organic matter was found, and significant autochthonous inputs were also present, especially at Site 545. Both strongly reduced and highly oxidized sediments have been found in the Cenozoic and Jurassic samples of Site 547. On the contrary, all the Cretaceous sections of Sites 547 and 545 are anoxic. Sediments from anoxic paleoenvironments are immature and have a high content of sterenes, diasterenes, steradienes, hopenes, and ßß hopanes. Samples from oxic paleoenvironments are mainly mature and their content of hopenes and steriod structures is below the detection level. Nevertheless, their hopane distributions have the immature ßß homologs as the predominant molecular markers. For Site 545 the most abundant molecular markers are ring A monoaromatic steranes, and their presence is attributed to microbial and chemical transformations during early diagenesis.

Organic carbon, freely extractable lipids and ketone recovery of ODP Leg 199 sediments

Six samples from Sites 1219 and 1221 ranging in age from early Eocene to early Oligocene were analyzed for freely extractable lipids to determine whether the low organic carbon (Corg) sediments of the Eocene equatorial Pacific (Corg content typically 0.03%) are appropriate for biomarker studies. Only one sample from the Oligocene equatorial Pacific (Sample 199-1219A-13H-3, 50-54 cm) contained any biomarkers of interest to paleoceanography. The only lipids identified in the remaining samples appear to be contaminants from drilling or subsequent handling. Sample 199-1219A-13H-3, 50-54 cm, contained alkenone biomarkers specific to haptophyte algae that are used for estimating past mean annual sea-surface temperature (maSST). If the Holocene calibration of maSST is appropriate for the Oligocene, the estimated equatorial temperature is >=28.3°C, or at least 3°C warmer than modern equatorial maSST at a similar longitude.

Lithology, stratigraphy, organic carbon content, extract and liquid chromatography yields, and Rock-Eval pyrolysis at DSDP Holes 75-530A and 75-532

Seventeen sediment samples of Albian-Cenomanian to early Pliocene age from DSDP Hole 530A in the Angola Basin and six sediment samples of early Pliocene to late Pleistocene age from the Walvis Ridge were investigated by organic geochemical methods, including organic carbon determination, Rock-Eval pyrolysis, gas chromatography and combined gas chromatography/mass spectrometry of extractable hydrocarbons, and kerogen microscopy. The organic matter in all samples is strongly influenced by a terrigenous component from the nearby continent. The amount of marine organic matter present usually increases with the total organic carbon content, which reaches an extreme value of more than 10% in a Cenomanian black shale from Hole 530A. At Site 530 the extent of preservation of organic matter in the deep sea sediments is related to mass transport down the continental slope, whereas the high organic carbon contents in the sediments from Site 532 reflect both high bioproductivity in the Benguela upwelling regime and considerable supply of terrigenous organic matter. The maturation level of the organic matter is low in all samples.

Geochemistry, lithology and maceral analysis at DSDP Hole 71-511

The quantity, type, and maturity of the organic matter in Recent through Upper Jurassic sediments from the Falkland Plateau, DSDP Site 511, have been determined. Sediments were investigated for their hydrocarbon potential by organic carbon and Rock-Eval pyrolysis. Kerogen concentrates were prepared and analyzed in reflected and transmitted light to determine vitrinite reflectance and maceral content. Total extractable organic compounds were analyzed for their elemental composition, and the fraction of the nonaromatic hydrocarbons was determined by capillary column gas chromatography and combined gas chromatography/mass spectrometry. Three main classes of organic matter can be determined at DSDP Site 511 by a qualitative and quantitative evaluation of microscopic and geochemical results. The Upper Jurassic to lower Albian black shales contain high amounts of organic matter of dominantly marine origin. The content of terrigenous organic matter increases at the base of the black shales, whereas the shallowest black shales near the Aptian/Albian boundary are transitional in composition, with increasing amounts of inert, partly oxidized organic matter which is the dominant component in all Albian through Tertiary sediments investigated. The organic matter in the black shales has a low level of maturity and has not yet reached the onset of thermal hydrocarbon generation. This is demonstrated by the low amounts of total extractable organic compounds, low percentages of hydrocarbons, and the pattern and composition of nonaromatic hydrocarbons. The observed reflectance of huminite and vitrinite particles (between 0.4% and 0.5% Ro at bottom-hole depth of 632 m) is consistent with this interpretation. Several geochemical parameters indicate, however, a rapid increase in the maturation of organic matter with depth of burial. This appears to result from the relatively high heat flow observed at Site 511. If we relate the level of maturation of the black shales at the bottom of Hole 511 to their present shallow depth of burial, they appear rather mature. On the basis of comparisons with other sedimentary basins of a known geothermal history, a somewhat higher paleotemperature gradient and/or additional overburden are required to give the observed maturity at shallow depth. A comparison with contemporaneous sediments of DSDP Site 361, Cape Basin, which was the basin adjacent and to the north of the Falkland Plateau during the early stages of the South Atlantic Ocean, demonstrates differences in sedimentological features and in the nature of sedimentary organic matter. We interpret these differences to be the result of the different geological settings for Sites 361 and 511.

Gas hydrate structures and C1-C5 hydrocarbons at individual sites in the Gulf of Mexico

Gas hydrate samples from various locations in the Gulf of Mexico (GOM) differ considerably in their microstructure. Distinct microstructure characteristics coincide with discrete crystallographic structures, gas compositions and calculated thermodynamic stabilities. The crystallographic structures were established by X-ray diffraction, using both conventional X-ray sources and high-energy synchrotron radiation. The microstructures were examined by cryo-stage Field-Emission Scanning Electron Microscopy (FE-SEM). Good sample preservation was warranted by the low ice fractions shown from quantitative phase analyses. Gas hydrate structure II samples from the Green Canyon in the northern GOM had methane concentrations of 70-80% and up to 30% of C2-C5 of measured hydrocarbons. Hydrocarbons in the crystallographic structure I hydrate from the Chapopote asphalt volcano in the southern GOM was comprised of more than 98% methane. Fairly different microstructures were identified for those different hydrates: Pores measuring 200-400 nm in diameter were present in structure I gas hydrate samples; no such pores but dense crystal surfaces instead were discovered in structure II gas hydrate. The stability of the hydrate samples is discussed regarding gas composition, crystallographic structure and microstructure. Electron microscopic observations showed evidence of gas hydrate and liquid oil co-occurrence on a micrometer scale. That demonstrates that oil has direct contact to gas hydrates when it diffuses through a hydrate matrix.

Sedimentary climate indicators of sediment core MD08-3167 and GeoB1711-4, southwestern Africa

The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes contradictory. Here we present a record of leaf-wax dD and View the MathML source taken from a marine sediment core at 23°S off the coast of Namibia to reconstruct the hydrology and C3 versus C4 vegetation of southwestern Africa over the last 140 000 years (140 ka). We find lower leaf-wax dD and higher View the MathML source (more C4 grasses), which we interpret to indicate wetter Southern Hemisphere (SH) summer conditions and increased seasonality, during SH insolation maxima relative to minima and during the last glacial period relative to the Holocene and the last interglacial period. Nonetheless, the dominance of C4 grasses throughout the record indicates that the wet season remained brief and that this region has remained semi-arid. Our data suggest that past precipitation increases were derived from the tropics rather than from the winter westerlies. Comparison with a record from the Congo Basin indicates that hydroclimate in southwestern Africa has evolved in antiphase with that of central Africa over the last 140 ka.

Polymer-solvent interaction parameters of SBS rubbers by inverse gas chromatography measurements

The solubility parameters of two SBS commercial rubbers with different structures (lineal and radial), and with slightly different styrene content have been determined by inverse gas chromatography technique. The Flory–Huggins interaction parameters of several polymer–solvent mixtures have also been calculated. The influence of the polymer composition, the solvent molecular weight and the temperature over these parameters have been discussed; besides, these parameters have been compared with previous ones, obtained by intrinsic viscosity measurements. From the Flory–Huggins interaction parameters, the infinite dilution activity coefficients of the solvents have been calculated and fitted to the well-known NRTL model. These NRTL binary interaction parameters have a great importance in modelling the separation steps in the process of obtaining the rubber.

A technique for recursive invariance detection and selective program specialization

This paper presents a technique for achieving a class of optimizations related to the reduction of checks within cycles. The technique uses both Program Transformation and Abstract Interpretation. After a ñrst pass of an abstract interpreter which detects simple invariants, program transformation is used to build a hypothetical situation that simpliñes some predicates that should be executed within the cycle. This transformation implements the heuristic hypothesis that once conditional tests hold they may continué doing so recursively. Specialized versions of predicates are generated to detect and exploit those cases in which the invariance may hold. Abstract interpretation is then used again to verify the truth of such hypotheses and conñrm the proposed simpliñcation. This allows optimizations that go beyond those possible with only one pass of the abstract interpreter over the original program, as is normally the case. It also allows selective program specialization using a standard abstract interpreter not speciñcally designed for this purpose, thus simplifying the design of this already complex module of the compiler. In the paper, a class of programs amenable to such optimization is presented, along with some examples and an evaluation of the proposed techniques in some application áreas such as floundering detection and reducing run-time tests in automatic logic program parallelization. The analysis of the examples presented has been performed automatically by an implementation of the technique using existing abstract interpretation and program transformation tools.

Simultaneous determination of multiclass emerging contaminants in aquatic plants by ultrasound assisted matrix solid phase dispersion and GC-MS

A multiresidue method was developed for the simultaneous determination of 31 emerging contaminants (pharmaceutical compounds, hormones, personal care products, biocides and flame retardants) in aquatic plants. Analytes were extracted by ultrasound assisted-matrix solid phase dispersion (UA-MSPD) and determined by gas chromatography-mass spectrometry after sylilation. The method was validated for different aquatic plants (Typha angustifolia, Arundo donax and Lemna minor) and a semiaquatic cultivated plant (Oryza sativa) with good recoveries at concentrations of 100 and 25 ng g-1 wet weight, ranging from 70 to 120 %, and low method detection limits (0.3 to 2.2 ng g-1 wet weight). A significant difference of the chromatographic response was observed for some compounds in neat solvent versus matrix extracts and therefore quantification was carried out using matrix-matched standards in order to overcome this matrix effect. Aquatic plants taken from rivers located at three Spanish regions were analyzed and the compounds detected were parabens, bisphenol A, benzophenone-3, cyfluthrin and cypermethrin. The levels found ranged from 6 to 25 ng g-1 wet weight except for cypermethrin that was detected at 235 ng g-1 wet weight in Oryza sativa samples.