Showing papers by "Geological Survey of Denmark and Greenland published in 2007"

Uncertainty in the environmental modelling process - A framework and guidance

Abstract: A terminology and typology of uncertainty is presented together with a framework for the modelling process, its interaction with the broader water management process and the role of uncertainty at different stages in the modelling processes. Brief reviews have been made of 14 different (partly complementary) methods commonly used in uncertainty assessment and characterisation: data uncertainty engine (DUE), error propagation equations, expert elicitation, extended peer review, inverse modelling (parameter estimation), inverse modelling (predictive uncertainty), Monte Carlo analysis, multiple model simulation, NUSAP, quality assurance, scenario analysis, sensitivity analysis, stakeholder involvement and uncertainty matrix. The applicability of these methods has been mapped according to purpose of application, stage of the modelling process and source and type of uncertainty addressed. It is concluded that uncertainty assessment is not just something to be added after the completion of the modelling work. Instead uncertainty should be seen as a red thread throughout the modelling study starting from the very beginning, where the identification and characterisation of all uncertainty sources should be performed jointly by the modeller, the water manager and the stakeholders.

Ancient Biomolecules from Deep Ice Cores Reveal a Forested Southern Greenland

Abstract: It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.

Leaching of estrogenic hormones from manure-treated structured soils.

Abstract: The threat to the aquatic environment posed by root zone leaching of estrogens from manure-treated fields has hitherto been overlooked. The steroid hormones 17beta-estradiol (E2) and its degradation product estrone (E1) are of particular environmental concern as both are abundant in slurryfrom pregnant and cycling pigs and both are potential endocrine disruptors (lowest observable effect level (LOEL) 14 and 3.3 ng/L, respectively). The present one-year study examines the transport of E1 and E2 from manure to tile drainage systems at two field sites on structured, loamy soil. The estrogens leached from the root zone to tile drainage water in concentrations exceeding the LOEL for as long as 3 months after application, with the maximum recorded concentration of E1 and E2 being 68.1 and 2.5 ng/ L, respectively. Transport of estrogens from the soil to the aquatic environment was governed by pronounced macropore flow and consequent rapid movement of the estrogens to the tile drains. These findings suggest that the application of manure to structured soils poses a potential contamination risk to the aquatic environment with estrogen, particularly when manure is applied to areas where the majority of streamwater derives from drainage water.

Forest fire and climate change in western North America: insights from sediment charcoal records

Abstract: Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and vegetation. We highlight several records from western North America and their relevance in reconstructing historical forest dynamics, fire-climate relationships, and feedbacks between vegetation and fire under climate change. Climatic effects on fire regimes are evident in many regions, but comparisons of paleo-fire records sometimes show a lack of synchrony, indicating that local factors substantially affect fire occurrence, even over long periods. Furthermore, the specific impacts of vegetation change on fire regimes differ among regions with different vegetation histories. By documenting the effects on fire patterns of major changes in climate and vegetation, paleo-fire records can be used to test the mechanistic models required for the prediction of future variations in fire.

Public participation modelling using Bayesian networks in management of groundwater contamination

Abstract: Negotiation and active involvement with participation of water managers, experts, stakeholders and representatives of the general public requires decision support tools (Environmental Decision Support Systems; EDSS) that build on transparency and flexibility in order to reach sound action plans and management instruments. One possible EDSS for active involvement of stakeholders is application of Bayesian networks (Bns). The paper gives an example of a case study (The Danish case) where farmers and hydrologists disputed the degree to which pesticide application affected the quality of deep groundwater. Instead of selecting one opinion or another, the decision was made to include both in the Bns. By adopting this approach, it was possible to view the results from either point of view, accepting the reality of the situation, not becoming mired in an insoluble conflict, and in this way laying the foundation for future compromises. The paper explores Bns as a tool for acting on and dealing with management of groundwater protection. Bns allow stakeholders' divergent values, interests and beliefs to be surfaced and negotiated in participatory processes for areas where conventional physically based groundwater models are insufficient due to lack of data, physical understanding, flexibility or lack of integration capability. In this way, the agency will be able to address the institutional arrangement influencing groundwater protection in all its complexity.

Consistent olivine Mg# in cratonic mantle reflects Archean mantle melting to the exhaustion of orthopyroxene

Abstract: Shallow (garnet-free), depleted cratonic mantle, occurring as xenoliths in kimberlites and alkaline basaltic lavas, has a high Mg# (100 × Mg/(Mg + Fe) > 92) and is poor in Al and Ca compared to off-cratonic mantle. Here we compile data for many suites of shallow cratonic mantle xenoliths worldwide, and demonstrate a remarkably small range in their olivine Mg#, with an average of ≈92.8. Via comparison with data for experimental melting of mantle peridotite compositions, we explain consistent olivine Mg# as the result of mantle melting and melt extraction to the point of orthopyroxene exhaustion, leaving a nearly monomineralic olivine residue.

Diffuse PAH contamination of surface soils: environmental occurrence, bioavailability, and microbial degradation

Abstract: The purpose of this review is to recognize the scientific and environmental importance of diffuse pollution with polycyclic aromatic hydrocarbons (PAHs). Diffuse PAH pollution of surface soil is characterized by large area extents, low PAH concentrations, and the lack of point sources. Urban and pristine topsoils receive a continuous input of pyrogenic PAHs, which induces a microbial potential for PAH degradation. The significance of this potential in relation to black carbon particles, PAH bioaccessibility, microbial PAH degradation, and the fate of diffuse PAHs in soil is discussed. Finally, the state-of-the-art methods for future investigations of the microbial degradation of diffuse PAH pollution are reviewed.

Quaternary glaciation history and glaciology of Jakobshavn Isbrae and the Disko Bugt region, West Greenland : a review

Abstract: The Disko Bugt region in central West Greenland is characterised by permanent ice streams, of which Jakobshavn Isbrae is by far the most important. The first thorough studies on the glaciology of the region were conducted over 150 years ago by H.J. Rink, who introduced the terms 'ice streams' and 'Inland Ice'. Rink's work inspired new field work, which has continued to the present, and the long series of observations are unique for an Arctic region. Cooling during the Cenozoic led to ice-sheet growth in Greenland. A number of interglacial occurrences have been reported from the Disko Bugt region, and during the penultimate glacial stage, the Greenland ice-sheet margin extended to the shelf break. During the last glacial maximum, the ice margin probably extended only to the inner part of the banks on the continental shelf, and large floating glaciers may have been present at this time. During the Younger Dryas cold period, the ice margin may have been located at a marked basalt escarpment west of Disko Bugt. Disko Bugt was deglaciated rapidly in the early Holocene, around 10 500–10 000 years before present (10.5–10 ka B.P.), but when the ice margin reached the eastern shore of the bay, recession paused, and major moraine systems were formed. With renewed recession, the present ice-margin position was attained around 8–6 ka B.P., and by c. 5 ka B.P. the ice margin was located east of its present position. The subsequent Neoglacial readvance generally reached a maximum during the Little Ice Age, around AD 1850. This was followed by recession that has continued to the present day. The relative sea-level history shows a rapid sea-level fall in the early Holocene, and a slow rise in the late Holocene. This development mainly reflects a direct isostatic response to the ice-margin history. Jakobshavn Isbrae is the main outlet from the Greenland ice sheet. It drains c. 6.5% of the present Inland Ice, and produces c. 35–50 km3 of icebergs per year, corresponding to more than 10% of the total output of icebergs from the Inland Ice. The velocity of the central part of the ice stream at the front has been around 7 km/year since records began, but has nearly doubled in recent years. Other calf-ice producing glacier outlets in Disko Bugt produce c. 18 km3 per year. The large calf-ice production of Jakobshavn Isbrae may have been initiated at about 8 ka B.P. when the glacier front receded from the iceberg bank (Isfjeldsbanken) near Ilulissat. Ice streams in inner and outer Egedesminde Dyb may have been active during the early Holocene and during the last glacial maximum.

Regional Differences in Climate Change Impacts on Groundwater and Stream Discharge in Denmark

Abstract: Regional impact studies of the effects of future climate change are necessary because projected changes in meteorological variables vary regionally, and different hydrological systems can react in various ways to the same changes. In this study the effects of climate change on groundwater recharge, storage, and discharge to streams are compared in two geologically and climatologically different regions in Denmark. Outputs are used for the periods 1961 to 1990 and 2071 to 2100 from a regional climate model representing the Intergovernmental Panel on Climate Change (IPCC) scenarios A2 and B2. A physically based, distributed hydrological model simulates changes in groundwater head, recharge, and discharge. Precipitation, temperature, and reference evapotranspiration increased for both the A2 and B2 scenarios. This results in a significant increase in mean annual net precipitation, but with decreased values in the summer months. The magnitude of the hydrological response to the simulated climate change is highly dependent on the geological setting of the model area. In the Jylland area, characterized by sandy top soils and large interconnected aquifers, groundwater recharge increased significantly, resulting in higher groundwater levels and increasing groundwater–river interaction. On Sjaelland, where the topsoil is dominated by low-permeability soils and the aquifers are protected by thick clay layers of regional extent, only minor changes in groundwater levels are predicted. The primary effect in this area is the change in stream discharge, caused by changes in drain flow and overland flow, with up to 50% increase in winter and 50% decrease in summer. This study shows the added value of studying different climate scenarios and hydrological systems, so that the simulated effects can be compared both qualitatively and quantitatively.

Hydrography and climate of the last 4400 years in a SW Greenland fjord: implications for Labrador Sea palaeoceanography

Abstract: A multiproxy record including benthic foraminifera, diatoms and XRF data of a marine sediment core from a SW Greenland fjord provides a detailed reconstruction of the oceanographic and climatic var...

Comparison of pressure‐saturation characteristics derived from computed tomography and lattice Boltzmann simulations

Abstract: [1] A Shan-Chen–type multiphase lattice Boltzmann (LB) model was applied to observed computed microtomography data from water-air and water-Soltrol displacement experiments in a glass bead porous medium. Analysis of the Bond, Reynolds, and Capillary numbers for these systems showed that capillary forces were dominant removing the need to model viscous, gravitational, and density effects. A numerical parameterization of the LB model yielded lattice surface tension and contact angle, and appropriate pressure boundary conditions. Two scaling relations provided a link between lattice pressure and physical pressure and lattice time and physical time. Results showed that there was a good match between measured and simulated pressure-saturation data for the water-air system, but that there were large differences between the simulations and observations for the water-Soltrol system. The discrepancies for the water-Soltrol system were probably due to inconsistencies between experimental conditions and simulated conditions such as nonzero contact angle in the experiments. Analysis of saturation profiles indicated increasing saturation near the wetting boundary and decreasing saturations near the nonwetting boundary. We attribute these saturation transitions to pore-neck and percolation effects. While computationally intensive, results of this study were very encouraging for the application of LB simulations to microscale interfacial phenomena. Future studies will carry out a further validation in terms of interfacial areas, contact lines, and fluid distributions.

Mesozoic–Cenozoic exhumation events in the eastern North Sea Basin: a multi‐disciplinary study based on palaeothermal, palaeoburial, stratigraphic and seismic data

Abstract: Four Mesozoic^Cenozoic palaeothermal episodes related to deeper burial and subsequent exhumation and one re£ecting climate change during the Eocene have been identi¢ed in a study of new apatite ¢ssion-track analysis (AFTA s ) and vitrinite re£ectance data in eight Danish wells.The study combined thermal-history reconstruction with exhumation studies based on palaeoburial data (sonic velocities) and stratigraphic and seismic data. Mid-Jurassic exhumation (ca. 175 Ma) was caused by regional doming of the North Sea area, broadly contemporaneous with deep exhumation in Scandinavia. A palaeogeothermal gradient of 451 Ck m � 1 at that time may be related to a mantle plume rising before rifting in the North Sea. Mid-Cretaceous exhumation aiecting the Sorgenfrei^Tornquist Zone is probably related to late Albian tectonic movements (ca.100 Ma).The Sole Pit axis in the southern North Sea experienced similar inversion and this suggests a plate- scale response along crustal weakness zones across NW Europe. Mid-Cenozoic exhumation aiected the eastern North Sea Basin and the onset of this event correlates with a latest Oligocene unconformity (ca. 24 Ma), which indicates a major Scandinavian uplift phase.The deeper burial that caused the late Oligocene thermal event recognized in the AFTA data re£ect progradation of lower Oligocene wedges derived from the uplifting Scandinavian landmass.The onset of Scandinavian uplift is represented by an earliest Oligocene unconformity (ca. 33 Ma). Late Neogene exhumation aiected the eastern (and western) North Sea Basin including Scandinavia.The sedimentation pattern in the central North Sea Basin shows that this phase began in the early Pliocene (ca. 4 Ma), in good agreement with the AFTA data. These three phases of Cenozoic uplift of Scandinavia also aiected the NE Atlantic margin, whereas an intra-Miocene unconformity (ca.15 Ma) on the NE Atlantic margin re£ects tectonic movements of only minor amplitude in that area.The study demonstrates that only by considering episodic exhumation as an inherent aspect of the sedimentary record can the tectonic evolution be accurately reconstructed.

The importance of alternative conceptual models for simulation of concentrations in a multi-aquifer system

Abstract: Four different conceptual models based on alternative geological interpretations were formulated for a shallow 600 km2 aquifer system in Denmark comprising Quaternary deposits. Each of the four models was calibrated against groundwater heads and discharge measurements through inverse modeling. Subsequently, the transport capabilities of the four models were compared to 32 concentration measurements of environmental tracers (tritium 3H, helium-3 3He, chlorofluorocarbons CFC11, CFC12 and CFC113). The flow simulations showed only minor differences in spatial head distribution associated with alternative conceptualizations despite the complexity of the aquifer system and the significant differences in geological interpretations. The models, however, showed major differences in predictions of the age of the groundwater and environmental tracer concentrations, differences that are seen as an effect of model structure uncertainty, because no additional calibrations to these data were performed. A single conceptualization may be adequate in characterizing the natural behavior of a field system after calibration, because the calibration procedure is able to compensate for errors in the data or in the conceptual model through biased parameter values. However, once extrapolation beyond the calibration base is attempted, different conceptual model formulations result in significantly different results. Consequently, it is crucial to take model conceptual uncertainty into account when making predictions beyond the calibration base.

A methodology to support multidisciplinary model-based water management

Abstract: Quality assurance in model based water management is needed because of some frequently perceived shortcomings, e.g. a lack of mutual understanding between modelling team members, malpractice and a tendency of modellers to oversell model capabilities. Initiatives to support quality assurance focus on single domains and often follow a textbook approach with guidelines and checklists. A modelling process involves a complex set of activities executed by a team. To manage this complex, usually multidisciplinary process, to guide users through it and enhance the reproducibility of modelling work a software product has been developed, aiming at supporting the full modelling process by offering an ontological knowledge base (KB) and a Modelling Support Tool (MoST). The KB consists of a generic part for modelling, but also parts specific for various water management domains, for different types of users and for different levels of modelling complexity. MoST's guiding component filters relevant knowledge from the KB depending on the user profile and needs. Furthermore, MoST supports different types of users by monitoring what they actually do and by producing customized reports for diverse audiences. In this way MoST facilitates co-operation in teams, modelling project audits and re-use of experiences of previous modelling projects.

Degradation and Mineralization of Nanomolar Concentrations of the Herbicide Dichlobenil and Its Persistent Metabolite 2,6-Dichlorobenzamide by Aminobacter spp. Isolated from Dichlobenil-Treated Soils

Abstract: Each year, millions of tons of xenobiotic compounds are applied globally as pesticides in agricultural production and in consolidated urban areas, along railways and roads and within farmyards. As an outcome of this extensive environmental input, natural water in rivers, lakes, and aquifers has been contaminated with trace amounts of pesticide residues. In Denmark, where more than 99% of the drinking water originates from groundwater, the detection of pesticide residues above the European Commission (EC) threshold limit of 0.1 μg liter−1 has resulted in the costly closure of numerous groundwater abstraction wells (29). Not only are the pesticides themselves monitored, but selected stable metabolites are also included, and often these are detected more frequently than the pesticide itself (3). The most commonly encountered pesticide residue in Danish groundwater is 2,6-dichlorobenzamide (BAM). BAM is a metabolite produced from partial degradation of the benzonitrile herbicide 2,6-dichlorobenzonitrile (dichlobenil) (1, 9, 16) and is often highly persistent in the environment. Dichlobenil is a broad-spectrum herbicide mostly used on nonagricultural areas, as well as in plant nurseries and fruit orchards. This herbicide was banned for use in Denmark in 1997, but BAM is still the main pesticide residue in Danish groundwater, with 19.7% of the abstraction wells analyzed in 2003 having detectable BAM concentrations and 8.1% of the wells containing BAM concentrations exceeding the EC threshold limit of 0.1 μg liter−1 for drinking water (3). Similar results were reported in 2003 in a monitoring program from Sweden (13), and BAM has additionally been detected in groundwater in The Netherlands, Germany, and Italy (18, 42, 44). A potential for partial degradation of the herbicide dichlobenil to BAM has been measured in various soils and subsurface sediments, with estimated half-lives ranging from 106 to 2,079 days (6, 8, 16, 41). Also, 2,6-dichlorobenzoic acid, another known metabolite from dichlobenil, has been measured in dichlobenil-treated soils (8, 24) and in groundwater samples (3, 18). Two additional metabolites, ortho-chlorobenzamide and ortho-chlorobenzoic acid, have been detected in laboratory experiments with dichlobenil-treated soils (8). The metabolite BAM appears to be much more persistent than dichlobenil itself, and several studies have reported no apparent degradation of BAM in soils (1, 6, 8, 16, 40, 41), aquifer sediments (2, 6, 36, 37), or bacterial isolates (9, 43). Little is therefore known about the environmental degradation of BAM. We are interested in using degradative bacteria for remediation of groundwater contaminated with low concentrations of BAM, and we therefore recently initiated a large-scale screening of dichlobenil-treated areas to locate soils capable of rapid mineralization of BAM (10, 25). These efforts have pinpointed 6 soils that have a potential for mineralization of [ring-U-14C]BAM to 14CO2, out of a total of 79 samples screened for mineralization activity, obtained from 39 different Danish locations previously exposed to dichlobenil. One of the soils with a potential for BAM mineralization but with no evident dichlobenil mineralization was recently used to enrich and isolate a BAM-mineralizing bacterium identified as an Aminobacter isolate, designated strain ASI1 (25). A second soil sampled from the courtyard of a former plant nursery located above a BAM-contaminated aquifer had a unique ability to mineralize both BAM and [ring-U-14C]dichlobenil to 14CO2 (25), and we later succeeded in obtaining stable BAM-mineralizing enrichment cultures (10), but isolation of degradative bacteria was not achieved. In this study we revived one of these enrichment cultures and isolated a BAM- and dichlobenil-mineralizing Aminobacter sp. strain (designated strain MSH1). This strain is closely related to our BAM-mineralizing Aminobacter sp. strain ASI1, and these two strains along with selected Aminobacter type strains were compared with regard to their taxonomy, degradative capacity toward dichlobenil and related compounds, and ability to degrade and mineralize low concentrations of BAM and dichlobenil.

A mid-Archaean island arc complex in the eastern Akia terrane, Godthåbsfjord, southern West Greenland

Abstract: A relict oceanic island arc complex in the eastern Akia terrane, Godthabsfjord, southern West Greenland, constitutes a magmatic and geotectonic link between c . 3.05–3.0 Ga tonalitic orthogneiss and enclaves of older supracrustal amphibolite. The relict arc forms isoclinally folded panels of volcaniclastic meta-andesite with major and trace element island arc signatures, intercalated with volcano-sedimentary schist, tholeiitic amphibolite and opx-rich cumulate rocks. A zircon U–Pb age of 3071 ± 1 Ma obtained from a volcano-sedimentary schist is marginally older than the main orthogneisses and is the first depositional age reported from a supracrustal rock within Akia terrane. Granite sheets were emplaced at c . 3005–2980 Ma synkinematically with the isoclinal folding, and were followed by peak metamorphism at 2990–2970 Ma with substantial recrystallization of volcanic zircon and mobility of large-ion lithophile elements. The identification of the arc complex provides new insight into mid-Archaean continental crustal accretion in West Greenland, and substantiates previous ideas that the orthogneisses are products of slab melting in convergent plate-tectonic settings. The presence of the arc complex also implies that Archaean high-grade orthogneiss–amphibolite associations may not represent plate-tectonic environments distinct from granite–greenstone associations, but expose deeper sections of the same convergent systems.

Strong Impact on the Polycyclic Aromatic Hydrocarbon (PAH)-Degrading Community of a PAH-Polluted Soil but Marginal Effect on PAH Degradation when Priming with Bioremediated Soil Dominated by Mycobacteria

Abstract: Bioaugmentation of soil polluted with polycyclic aromatic hydrocarbons (PAHs) is often disappointing because of the low survival rate and low activity of the introduced degrader bacteria. We therefore investigated the possibility of priming PAH degradation in soil by adding 2% of bioremediated soil with a high capacity for PAH degradation. The culturable PAH-degrading community of the bioremediated primer soil was dominated by Mycobacterium spp. A microcosm containing pristine soil artificially polluted with PAHs and primed with bioremediated soil showed a fast, 100- to 1,000-fold increase in numbers of culturable phenanthrene-, pyrene-, and fluoranthene degraders and a 160-fold increase in copy numbers of the mycobacterial PAH dioxygenase gene pdo1. A nonpolluted microcosm primed with bioremediated soil showed a high rate of survival of the introduced degrader community during the 112 days of incubation. A nonprimed control microcosm containing pristine soil artificially polluted with PAHs showed only small increases in the numbers of culturable PAH degraders and no pdo1 genes. Initial PAH degradation rates were highest in the primed microcosm, but later, the degradation rates were comparable in primed and nonprimed soil. Thus, the proliferation and persistence of the introduced, soil-adapted degraders had only a marginal effect on PAH degradation. Given the small effect of priming with bioremediated soil and the likely presence of PAH degraders in almost all PAH-contaminated soils, it seems questionable to prime PAH-contaminated soil with bioremediated soil as a means of large-scale soil bioremediation.

A Textural Record of Solidification and Cooling in the Skaergaard Intrusion, East Greenland.

Abstract: The clinopyroxene^plagioclase^plagioclase dihedral angle, cpp, in gabbroic cumulates records the time-integrated thermal history in the sub-solidus and provides a measure of textural maturity. Variations in cpp through the Layered Series of the Skaergaard intrusion, East Greenland, demonstrate that the onset of crystallization of clinopyroxene (within LZa), Fe^Ti oxides (at the base of LZc) and apatite (at the base of UZb) as liquidus phases in the bulk magma is recorded by a stepwise increase in textural maturity, related to an increase in the contribution of latent heat to the total heat loss to the surroundings and a reduction in the specific cooling rate at the crystallization front of the intrusion. The onset of both liquidus Fe^Ti oxide and apatite crystallization is marked by a transient increase in textural maturity, probably linked to overstepping before nucleation. Textural maturation at pyroxene^plagioclase^plagioclase triple junctions effectively ceases in the uppermost parts of the Layered Series as a result of the entire pluton cooling below the closure temperature for dihedral angle change, which is 10758C. Solidification of the Layered Series of the Skaergaard intrusion occurred via the upwards propagation of a mush zone only a few metres thick.

Seismic study of the transform‐rifted margin in Davis Strait between Baffin Island (Canada) and Greenland: What happens when a plume meets a transform

Abstract: [ 1] The Davis Strait transform margin was studied using a 630-km-long wide-angle reflection/ refraction seismic transect extending from SE Baffin Island to Greenland. Dense airgun shots were recorded by 28 ocean bottom seismometers deployed along the line. A P wave velocity model was developed from forward and inverse modeling of the wide-angle data and incorporation of coincident deep multichannel reflection seismic data. Off Baffin Island in the Saglek Basin, 7 to 11-km-thick two-layered continental crust (5.8 - 6.6 km/s) is observed. Off Greenland, continental crust is divided into three layers (5.4 - 6.8 km/s) with a maximum thickness of 20 km. Farther offshore Greenland the crust thins to 7 - 12 km and the lower crust disappears. Between the continental blocks a 140-km-wide zone with oceanic crust ( layer 2 is 5.4 - 6.2 km/s and layer 3 is 6.7 - 7.0 km/s) is located. The western half of this zone is interpreted to be part of a volcanic margin with seaward dipping reflectors; the eastern part is associated with the Ungava fault zone (UFZ), the major transform fault in Davis Strait. The UFZ thus acted as leaky transform fault during phases of transtension. Southward flow of material from the Iceland plume created a 4 to 8-km-thick underplated layer (7.4 km/s) beneath the thinned portions of the continental crust and beneath previously emplaced oceanic crust. Plume related Paleogene volcanism is indicated by an up to 4-km thick layer (4.3 - 5.8 km/s) with basalts and interbedded sediments that can be traced from SE Baffin Island 400 km toward the east.

Lithostratigraphy of the Palaeogene – Lower Neogene succession of the Danish North Sea

Abstract: As a result of a lithological, sedimentological and biostratigraphic study of well sections from the Danish sector of the North Sea, including some recently drilled exploration wells on the Ringkobing–Fyn High, the lithostratigraphic framework for the siliciclastic Palaeogene to Lower Neogene sediments of the Danish sector of the North Sea is revised. The sediment package from the top of the Chalk Group to the base of the Nordland Group is subdivided into seven formations containing eleven new members. The existing Vale, Lista, Sele, Fur, Balder, Horda and Lark Formations of previously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector at formation level. Bor is a new sandstone member of the Vale Formation. The Lista Formation is subdivided into three new mudstone members: Vile, Ve and Bue, and three new sandstone members: Tyr, Idun and Rind. Kolga is a new sandstone member of the Sele Formation. Hefring is a new sandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of the Lark Formation. Danish reference sections are established for the formations, and the descriptions of their lithology, biostratigraphy, age and palaeoenvironmental setting are updated.

Source Rock Evaluation of Coals from the Lower Maastrichtian Mamu Formation, se Nigeria

Abstract: The Lower Maastrichtian Mamu Formation in the Anambra Basin (SE Nigeria) consists of a cyclic succession of coals, carbonaceous shales, silty shales and siltstones interpreted as deltaic deposits. Sub-bituminous coals within this formation are distributed in a north-south trending belt from Enugu-Onyeama to Okaba in the north of the basin. Maceral analyses showed that the coals are dominated by huminite with lesser amounts of liptinite and inertinite. Despite high liptinite contents in parts of the coals, an HI versus Tmax diagram and atomic H/C ratios of 0.80-0.90 and O/C ratios of 0.11-0.17 classify the organic matter in the coals as Type III kerogen. Vitrinite reflectance values (%Rr) of 0.44 to 0.6 and Tmax values between 417 and 429°C indicate that the coals are thermally immature to marginally mature with respect to petroleum generation. Hydrogen Index (HI) values for the studied samples range from 203 to 266 mg HC/g TOC and S1+S2 yields range from 141.12 to 199.28 mg HC/ g rock, suggesting that the coals have gas and oil-generating potential. Ruthenium tetroxide catalyzed oxidation (RTCO) of two coal samples confirms the oil-generating potential as the coal matrix contains a considerable proportion of long-chain aliphatics in the range C19-35. Stepwise artificial maturation by hydrous pyrolysis from 270°C to 345°C of two coal samples (from Onyeama, HI=247 mg HC/g TOC; and Owukpa, HI=206 mg HC/g TOC) indicate a significant increase in the S1 yields and Production Index with a corresponding decrease in HI during maturation. The Bitumen Index (BI) also increases, but for the Owukpa coal it appears to stabilize at a Tmax of 452-454°C, while for the Onyeama coal it decreases at a Tmax of 453°C. The decrease in BI suggests efficient oil expulsion at an approximate vitrinite reflectance of ∼I%Rr. The stabilization/decrease in BI is contemporaneous with a significant change in the composition of the asphaltene-free coal extracts, which pass from a dominance of polar compounds (∼77-84%) to an increasing proportion of saturated hydrocarbons, which at >330°C constitute around 30% of the extract composition. Also, the n-alkanes change from a bimodal to light-end skewed distribution corresponding to early mature to mature terrestrially sourced oil. Based on the obtained results, it is concluded that the coals in the Mamu Formation have the capability to generate and expel liquid hydrocarbons given sufficient maturity, and may have generated a currently unknown volume of liquid hydrocarbons and gases as part of an active Cretaceous petroleum system.

Foraminiferal reconstruction of mid-to late-Holocene ocean circulation and climate variability in Disko Bugt, West Greenland

Abstract: Benthic foraminifera from two cores collected from Disko Bugt, a large marine embayment in West Greenland, are used to investigate hydrographic changes during the mid to late Holocene. The records document fluctuations in the West Greenland Current (WGC) linked to large-scale changes in North Atlantic circulation and, for one core, impacts of local climate changes. In particular, changes in the cold East Greenland Current (EGC) and the warm, more saline Irminger Current (IC) influence the WGC and propagate into Disko Bugt. The cores record subsurface warming associated with the `Holocene Thermal Maximum' (HTM) from c. 6 to 5 ka cal. BP. Gradual cooling of WGC from 5 ka cal. BP was interrupted by an abrupt warm interval from 3.9 to 3.5 ka cal. BP, before cooling became more prominent from 3.5 to 2 ka cal. BP. This cold period corresponds to the well-documented Northern Hemisphere cooling of the neoglacial and we interpret it as reflecting enhanced flux from the EGC and reduced IC flux to the WGC in Disko B...