Initial Transgressive Phase of Leg 144 Guyots: Evidence of Extreme Sulfate Reduction

The initial transgressive phase at the Leg 144 Guyots is characterized by a typical association of sedimentary facies (from bottom to top): in situ weathered volcanic rocks; variegated clays, partly pyritic; gray clay, pyritic, homogeneous, or mottled; black clay, peaty, laminated, or bioturbated; and marine argillaceous limestone. Site 877 at Wodejebato Guyot represents the typical development of the initial transgressive phase. The black clay is rich in organic carbon (up to 40%) and sulfur (up to 25%). The organic matter is dominantly of terrestrial origin, but it has a significant marine, algal input. The variegated clays consist of a red, lower, sulfur-free part and a blue to gray-blue, sulfur-containing upper part. Organic carbon is not observed in this facies. The sulfur occurs as pyrite and organically bound sulfur. The isotope composition of pyrite varies from -50‰ to 0%e, which clearly points to bacterial sulfate reduction as the origin for the high sulfur content. Pyrite formation was limited by availability of reactive iron. Because of the origin of the clays as lateritic weathering products, the amount of reactive iron was high, and pyritization proceeded to high values. The following model is suggested for sulfur enrichment in the sediments at the initial transgressive phase: (1) marine flooding of an organic-rich back-reef mangroval swamp; (2) intense bacterial reduction of marine sulfate within the black clay; and (3) downward diffusion of H2S into the underlying clays, reduction of red iron oxides to blue-gray iron sulfides, and growth of pyrite

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Orthoceratit i olie - en specialitet fra Ordovicium ved Kinnekulle

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Holocene changes in atmospheric circulation recorded in the oxygen-isotope stratigraphy of lacustrine carbonates from northern Sweden

The oxygen-isotope composition of local precipitation (d18OP) is reconstructed from carbonate lake-sediment components in a sediment core covering the last 10000 calendar years from Lake Tibetanus, a small, hydrologically open, groundwater-fed lake in the Abisko area, northern Sweden. Comparison of the d18OP history with a pollen-based palaeotemperature record from the same core clearly reveals pronounced deviations from the normally expected temporal d18OP-temperature relation (so-called ‘Dansgaard relation’) that may be a function of changing oceanicity. The transition from relatively moist, maritime conditions in the early Holo cene to a much drier climate after 6500 cal. BP is re‘ ected by major changes in forest extent and composition as recorded by pollen and plant macrofossil data. At the time of maximum in‘ uence of westerly air-mass circulation (high zonal index) c. 9500 cal. BP, brought about by high summer insolation and enhanced meridi onal pressure gradients, d18OP at Lake Tibetanus was about 2 higher than would be predicted by the modern isotope-temperature relation. The occurrence of long-term changes in d18OP-temperature relations, which are more sensitive measures of palaeoclimate than either d18OP or temperature alone, needs to be taken into account when extracting palaeoclimatic information from continental oxygen-isotope records

Effect of sample treatment methods for PAH4 determination in cocoa

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and some have been reported to be present in cocoa. Therefore, PAHs determination in cocoa is very important. In this study, a simple procedures based on maceration extraction, solid phase extraction (SPE), saponification and high-performance liquid chromatography with fluorescence detection (HPLC-FLD) were presented for rapid PAH4 (sum of four different PAHs; benzo (a) anthracene, chrysene, benzo (b) fluoranthene, and benzo (a) pyrene) determination in cocoa samples (cocoa bean, cocoa nib and cocoa shell). The effect of using different sample extractions (different type of solvents and extraction time) and purification methods (different SPE treatments) were investigated. The most satisfactory recoveries (59.83 – 116.99% at concentration levels; 1.00, 5.00 and 10.00 µ/kg) and clean extracts were obtained by extracting the cocoa samples (cocoa nib, cocoa shell and whole cocoa bean) with hexane for two hours and purification with SPE using silica cartridge (cyclohexane as elution solvent). In this study, detection limit was in the range of 3.36 – 13.90 ng/kg thus, the method meets the Commission Regulation (EU) No. 836/2011 and may be useful to be applied for assessment of cocoa beans quality

Stratigraphy and palaeoceanography of upper Maastrichtian chalks, southern Danish Central Graben

Upper Maastrichtian chalks form important hydrocarbon reservoirs in the Danish sector of the North Sea and have been intensively studied, yet their lithological uniformity can frustrate attempts to develop a high-resolution stratigraphic subdivision and a genetic understanding of the factors controlling production and sedimentation of the pelagic carbonate ooze. Recent research into these topics, supported by the Danish Energy Authority, was carried out by the Geological Survey of Denmark and Greenland (GEUS) in collaboration with the Geological Institute, University of Copenhagen by means of a multidisciplinary study involvingquantitative/semiquantitative palynology, micropalaeontology (nannofossils, foraminifers) and isotope geochemistry, integrated with detailed sedimentology. Two key wells were selected, the M-10X well from the Dan Field and the E-5X well from the Tyra SE Field (Fig. 1), based on the extensive core coverage in these wells and on their position in the southern part of the Danish Central Graben where evidence of large-scale resedimentation (and consequent stratigraphic complexity) is uncommon within the Maastrichtian section. In focusing on such a pelagic carbonate system, the ultimate aim is a holistic understanding of the marine system including temperature variation, nutrient supply and distribution, salinity, watermass layering, circulation and oxygen distribution. All these factors influence organic productivity and thus the accumulation of biogenic sediment. This study concentrated on a number of palaeoceanographic signals that can be derived from the sedimentary record, summarised in Fig. 2. Planktonic organisms, both phytoplankton (e.g. coccolithophores, some dinoflagellates) and zooplankton (e.g. foraminifers) provide a record of conditions in the upper water masses, largely within the photic zone, while bottom conditions are indicated by epifaunal/infaunal organisms (e.g. benthic foraminifers) and bioturbation, and by the sedimentological evidence of depositional processes at the sea floor. On a larger scale, the input of terrestrial organic material relative to the marine component can provide an indirect measure of shoreline migration and thus relative sea-level change, a factor that is also reflected in the δ13C isotopic composition of the seawater, as recorded by the biogenic carbonate ooze