Landform development on moraines of the Klutlan Glacier,Yukon Territory,Canada

The landform evolution of the Klutlan moraines is described and explained primarily with respect to processes that cause voids in which debris is deposited. Morainal deposits of different ages provide examples of landforms at different stages of development, so that continuous ideal evolutionary sequences can be inferred. Specific features are classified as those on material of the same depositional age that develop mostly in a vertical direction with numerous topographic reversals, and those cross-cutting materials of different depositional age that develop primarily in a horizontal direction. The evolution of slopes is often terminated by their destruction as the underlying ice melts, but former slopes on morainal debris are traceable to ice-ridge slopes on the original glacier surface. The general process of evolution is one of downwasting by surficial icemelt, in which a grand topographic reversal takes place as the original ice mass with a gently convex surface melts to leave a basin floored by a concave mantle of morainal debris. The primary glacial process of melting differs from the primary karst process of solution, but many minor glacial processes and major glacial forms are similar to minor karst processes and major karst forms.     

Tectonic implications of the immobile trace‐element geochemistry of mafic rocks bounding the Wonaminta Block

The Wonaminta Block is bounded on its eastern and western margins by Lower Cambrian or upper Vendian intrusive and extrusive igneous rocks. The extrusive rocks include pillow lavas. Low‐grade metamorphism has not influenced the distribution of P2O3, Zr, Y, and Nb, but remobilization of Ti has occurred in rocks containing Ti within the oxide phases rather than in the silicate phases. Immobile trace‐element discrimination techniques indicate that the basalts on the western margin of the Wonaminta Block are alkaline whereas those on the eastern margin are tholeiitic. The possibility that these rocks represent petrological variants across an arc system is discussed.     

The relationships of population and forest trends

The relationship between national trends in forest area and population is reviewed at the global scale. Evidence of an inverse relationship is confirmed. The relationship, however, may have weakened in recent decades, and it has clearly undergone a reversal in some countries during the nineteenth to twentieth centuries. The theme of a changing relationship through time is thus developed, as is that of an asymmetrical relationship in the sense that the forest area is likely to stabilize before population. On the basis of modelling from the current demographic relationship, the global forest area should stabilize before the middle of the twenty-first century.     

On sheared passive continental margins

Studies in intra-continental and intra-oceanic shear zones reveal structures that may be developed during the formation of a sheared passive continental margin.During the intra-continental shear stage of margin development, rapid vertical movement of the crust may occur resulting in small, tectonically-active basins containing thick sedimentary sequences. At deeper levels in the continental crust, more plastic deformation may lead to a zone of strongly sheared rocks that widens downwards. The tectonic fabric in this zone may exert some control over the subsequent development of the continent-ocean transition under the influence of regional stresses.The thermal event related to asthenosphere upwelling at sheared margins is a transient one and thus of less effect than the event on rifted margins. Nevertheless, following the event the cooling and contraction of oceanic crust against the continent may throw the oceanic crust into tension and lead to normal, block faulting in the oceanic regions analogous to the faulting seen in oceanic fracture zones. The subsidence of oceanic crust as it ages at the margin will either drag down the adjacent continental crust or, more likely, cause the oceanic crust to slip down by normal faulting along the continent-ocean boundary. The kinds of compressional features observed in oceanic fracture zones may also occur at sheared margins.     

Mercury partition in the interface between a contaminated lagoon and the ocean: The role of particulate load and composition

After having estimated the patterns of flow to the ocean and found some seasonal and tidal differences, mainly with regard to the relative importance of dissolved and particulate fractions, mercury partitioning at the interface between a contaminated lagoon and the Atlantic Ocean was investigated during four tidal cycles in contrasting season and tidal regimes. Mercury was found to be located predominantely in the particulate fraction throughout the year, contributing to its retention within the system. Seasonal conditions, variations in marine and fluvial signals and processes affecting bed sediment resuspension influenced the character and concentration of suspended particulate matter in the water column. Variation in the nature, levels and partitioning of organic carbon in the particulate fraction affected levels of particulate mercury as well as mercury partitioning. These results highlight the dominant role of suspended particulate matter in the distribution of anthropogenic mercury and reinforce the importance of competitive behavior related to organic carbon in mercury scavenging.     

Apparent polar wander paths carboniferous through cenozoic and the assembly of Gondwana

Directions of magnetization observed from rock-units from a given continental block are conveniently summarized by a path of apparent polar wander (apw) relative to that block. This article documents apw paths for the major continental blocks spanning the interval from Late Carboniferous (approximately –300 Ma) to the present. It is shown that by passing moving windows of 30 or 40 Ma duration over the data an apw path can be obtained with little or no loss of features through smoothing. It also is shown that mean pole positions obtained using Fisher's statistics or by calculating modes do not differ significantly. In the analysis poor results are screened out by applying certain minimum reliability criteria. Unit weight is then given to each of the remaining results. No attempt has been made to weight the results differentially because of the risk of added subjectivity.The paths contain many interesting features. One is an interval of rapid apparent polar motion relative to all major land-masses that occurred sometime in the Late Permian and Triassic. The general form of these motions is roughly established, but their timing and detailed form is poorly known because of inadequacies in the paleomagnetic record. Although it is clear that the motions occurred sometime around the Paleozoic-Mesozoic boundary it is not known whether the motions are or are not contemporaneous from continent to continent.Apw paths are of great importance for many problems in geology and geophysics. As an example, the new paths are applied to the question of how should Gondwana be correctly assembled. The results show that the best available reconstruction is the 1937 assembly of Alex du Toit as quantified by Smith and Hallam, with a minor modification by Barton and Molnar for the fit of Australia and Antarctica. Assemblies, that place Antaretica to the south and wrap the Antarctic Peninsula around the southern Andes, are not supported by the paleomagnetic data. There are, however, several obscurities, which derive, it is argued, from the uncertainties in timing the Late Permian to Triassic transitions alluded to above.     

The isotopic composition of strontium and oxygen in lavas from St. Helena,South Atlantic

Strontium and oxygen isotope measurements on the alkali basalt-trachyte-phonolite suite of St. Helena show that some of the late-fractionated rocks are enriched in ⁸⁷Sr and depleted in ¹⁸O relative to the older basalts. The data rule out both the formation of the late-fractionated rocks by the partial melting of hydrothermally altered oceanic crust and the contamination of the volcanic rocks by oceanic sediment. It also appears to be incompatible with models based either on the melting of previously fractionated and crystallized liquids in the volcanic pile, or the long-term fractionation of lavas over several millions of years in a sub-volcanic magma chamber.It is concluded that hydrothermal interaction with meteoric water is the most important cause of the ¹⁸O depletion. If the interaction occurred at widely differing temperatures, and involved meteoric and seawaters, it might conceivably have caused both the oxygen and strontium isotope heterogeneities.     

Cosmology and cosmogony in a cyclic universe

In this paper we discuss the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. We discuss the origin of such a scalar field in the primary creation process first described by F. Hoyle & J. V. Narlikar forty years ago. It is shown that the creation processes which take place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts. The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydrogen burning in stars), and the origin of the lightest nuclei (H, D, He³ and He⁴). It also allows us to relate the large scale cyclic properties of the universe to events taking place in the nuclei of galaxies. Observational evidence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe. In the later parts of the paper we briefly discuss the major unsolved problems of this integrated cosmological and cosmogonical scheme — the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.     

Evaluation of the removal of heavy metals in a natural wetland impacted by mining activities in Mexico

This research is focused on evaluating heavy metals (Cd, Cu, Fe, Mn, Pb, and Zn) uptake and removal by Eleocharis ovata, Cyperus manimae, Typha dominguensis, and Pteridium aquilinum in a natural wetland impacted by mining activities. We analyzed heavy metals content and distribution in native plants, soils, and water of a semipermanent natural wetland in Taxco de Alarcón, Guerrero, and we also determined the physicochemical characteristics of the water. Translocation factor (TF) and bioconcentration factor (BCF) were evaluated. Results showed that physical and chemical conditions are favorable for plants development. Correlation analysis showed a good and positive relation (0.95) between Cu and Pb in soils and plants. In the analyzed matrices: Zn (0.62–2.20 mg/L) exceeded the permissible limits in water, high concentrations of Pb and Zn (26.57–525.67 and 266.67–983.33 mg/kg, respectively) were detected in the studied soils, and Pb exceeded the normal range for E. ovata and P. aquilinum in the analyzed plants. Uptake of heavy metals in the tissues of different species was found in the following order: root > leaf. Data of TF and BCF showed that E. ovata is a tolerant plant with respect to heavy metals exposure since TF value was greater than 1. This study showed that E. ovata could be considered as a bioaccumulator of heavy metals in contaminated soils.