Polycyclic aromatic hydrocarbons as evidence of hydrocarbon migration in marine and lagoon sediments of a recent rift zone (Skjálfandi and Öxarfjörður), Iceland

Polycyclic aromatic hydrocarbons (PAHs) content and distribution was studied in the northern part of modern rift zone. All samples analysed represent slightly altered clastic deposits and hot water discharging in springs and from wells. To study PAH in present-day gas emission traps with diatomite absorbent were installed in the Skógalón geothermal field. All samples were analysed by the method of Shpol'sky spectroscopy. Hydrothermally altered deposits show the highest amount of PAH. Data obtained allow to believe that the distribution of PAH is closely associated with the dynamics of the hydrothermal environment. The fissure formation and temperature fluctuation in hydrothermal systems can govern both the processes of PAH synthesis and sorption. The evidences of PAH migration up through the Skjálfandi and Öxarfjörður sedimentary basins show that hydrocarbons associate mainly with hydrothermal minerals and deep ground waters. Studying PAH associations can be used as an indicator of hydrocarbons distribution, ways of migration and possible zones of accumulation in the land and marine sedimentary basins in active and ancient rift zones of Iceland.     

Modelling Internal Solitary Waves in the Coastal Ocean

In the coastal oceans, the interaction of currents (such as the barotropic tide) with topography can generate large-amplitude, horizontally propagating internal solitary waves. These waves often occur in regions where the waveguide properties vary in the direction of propagation. We consider the modelling of these waves by nonlinear evolution equations of the Korteweg–de Vries type with variable coefficients, and we describe how these models are used to describe the shoaling of internal solitary waves over the continental shelf and slope. The theories are compared with various numerical simulations.     

Evolution of a Shallow Water Wave‐Dominated Shipwreck Site: Fougueux (1805), Gulf of Cadiz

The evolution of the shallow water wave‐dominated Fougueux wreck site in the Gulf of Cadiz was investigated through repeat bathymetric surveys, wave‐ and current‐velocity field measurements, and numerical modeling. This multidisciplinary approach was used to understand the relationships between scouring, morphodynamic change, and hydrodynamic forcing. Field experiments and numerical models indicate that wave processes dominate site evolution. Numerical model outputs indicate current velocity, bed shear stress, orbital velocity, and specially wave fraction breaking (with an increase of 45% and 135% for weak and significant storm conditions, respectively) are all amplified at the site. Scour pits 0.8 m depth inshore and 0.4 m depth offshore of the wreck are developed in response to hydrodynamic forcing. Time‐lapse bathymetric surveys quantify seasonal geomorphological change at the Fougueux. Up to 1.2 m of sediment is deposited and 0.7 m of sediment eroded in response to seasonal wave climate variation (an increase of 0.5 m for mean significant wave height, 0.9 m for significant wave height corresponding to 99% of nonexceedance probability, and 0.4 m·s⁻¹ for mean near‐bed orbital velocity during winter conditions). A two‐dimensional scour model reproduces observed seasonal scour changes. Results have direct applications at all stages of a wreck site investigation.     

Secular dynamics of S-type planetary orbits in binary star systems: applicability domains of first- and second-order theories

We analyse the secular dynamics of planets on S-type coplanar orbits in tight binary systems, based on first- and second-order analytical models, and compare their predictions with full N-body simulations. The perturbation parameter adopted for the development of these models depends on the masses of the stars and on the semimajor axis ratio between the planet and the binary. We show that each model has both advantages and limitations. While the first-order analytical model is algebraically simple and easy to implement, it is only applicable in regions of the parameter space where the perturbations are sufficiently small. The second-order model, although more complex, has a larger range of validity and must be taken into account for dynamical studies of some real exoplanetary systems such as \(\gamma \) Cephei and HD 41004A. However, in some extreme cases, neither of these analytical models yields quantitatively correct results, requiring either higher-order theories or direct numerical simulations. Finally, we determine the limits of applicability of each analytical model in the parameter space of the system, giving an important visual aid to decode which secular theory should be adopted for any given planetary system in a close binary.     

The Holocene vegetation history of the Khibiny Mountains: implications for the post‐glacial expansion of spruce and alder on the Kola Peninsula,northwestern Russia

Pollen and peat botanical investigations of the Lutnermayok peat bog, Kola Peninsula, northwestern Russia, were carried out, and 21 surface pollen samples were studied. Combined with previous studies our data form the basis for the vegetation history over the last 7000 yr of the Khibiny Mountains. Pinus sylvestris was the dominant species between 7000 and 5000 yr BP and Picea obovata penetrated to the Khibiny Mountains ca. 5500/5300 yr BP. Since 4500 yr BP, Picea replaced Pinus in major parts of the area and dominated the forest cover. Picea immigrated to the Kola Peninsula after 7000 yr BP. There were two paths of spruce migration: from the southeast and the southwest. Grey alder, Alnusincana, immigrated to the Kola Peninsula from the southwest and northwest about ca. 8000 yr BP. Grey alder has been restricted to its modern range since 4000 yr BP. The range of vertical movement of the treeline in Khibiny Mountains during the last 700 yr was 240–260 m, which corresponds to an amplitude of summer temperature change of 2°C. Copyright © 1999 John Wiley & Sons, Ltd.     

The role of inherited extensional fault segmentation and linkage in contractional orogenesis: a reconstruction of Lower Cretaceous inverted rift basins in the Eastern Cordillera of Colombia

Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.     

Simulation of spatially-distributed copper pollution in a large river basin using the ECOMAG-HM model

The semi-distributed physically-based model ECOMAG-HM was developed to simulate cycling of heavy metals in large river basins: on the surface, and in soil, groundwater and river water. The model was applied to study the spatial distribution and temporal dynamics of copper concentrations in watercourses of the Nizhnekamskoe Reservoir watershed in Russia. This watershed is characterized by high background concentrations of heavy metals due to wide occurrence of ore deposits and considerable concentrations of ore-parent elements in rocks. The model was found to adequately reproduce the spatial variation of the mean annual copper concentrations at different monitoring points of the river network. The mean annual specific copper washoff, with the surface and subsurface components of river runoff, and the total copper washoff from the watershed into the river network were calculated and mapped. The contributions of natural and anthropogenic factors to river water pollution by copper were evaluated.     

The anisotropic distribution of the dark energy within the scope of LRS Bianchi type I model

We investigate the anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with dark matter and anisotropic dark energy. We assume that the shear scalar \((\sigma )\) is proportional to expansion scalar \((\theta )\). A special law is introduced for two skewness parameters that describe the deviation of pressure from isotropy. This law can lead to models: the hybrid expansion, the big rip and the little rip. The behavior of the Universe is discussed depending on the numerical parameters of the models.     

Interacting dark sector and the coincidence problem within the scope of LRS Bianchi type I model

It is shown that a suitable interaction between dark energy and dark matter in locally rotationally symmetric (LRS) Bianchi-I space-time can solve the coincidence problem and not contradict the accelerated expansion of present Universe. The interaction parameters are estimated from observational data.     

Seasonal Variability of Polycyclic Aromatic Hydrocarbons (PAHs) in a Coastal Marine Area in the Northwestern Region of the Sea of Japan/East Sea (Possiet Bay)

Ocean Science Journal - Contamination by persistent organic pollutants including polycyclic aromatic hydrocarbons (PAHs) constitutes a major concern in relation to aquatic ecosystems. To study the...