Space-time analysis of the relative local secular variations of the geomagnetic field (1966–2005) along the Zgorzelec-Wiżajny profile

The Zgorzelec-Wiżajny profile cuts through the main European geotectonic units of the Palaeozoic Western and Central European Platform and the East European Craton, including the connecting Trans-European Suture Zone. The paper summarises 40 years of research on geomagnetic secular variations along the Zgorzelec-Wiżajny profile since 1966. It discusses methods of processing measurement records and presenting their results. The latter are presented against the background of the local geology and the crustal deep magnetic structure data. The hitherto method of variation analysis was modified to address a new trend in the geomagnetic secular variations that has emerged in the East European Craton during the last five years (2001–2005).     

Rare-gas dating,III. Evaluation of a double-spiking procedure for potassium-argon dating

A double-spike method for KAr dating is described. Use of long-lived³⁹Ar in addition to the usual³⁸Ar in the spike permits argon isotopic discrimination occurring after insertion of the spike to be monitored at the same time as ages are determined. A “bootstrap” (self-contained) method of calibrating the spike for isotopic composition is described which, when used appropriately, gives final ages which are independent of the published isotopic composition of the terrestrial atmospheric argon used as a comparison gas. The method calls for a mass spectrometer which resolves adjacent isotopes to a high degree. We have tested the method nevertheless with a mass spectrometer of relatively low resolving power, the AEI MS-10, and found it to be successful in part and without any disadvantages with respect to conventional techniques in those instances where the method fails because of insufficient resolution. That is, we find the discrimination factor inferred in runs on young rocks and blanks to be valid and useful. That factor changes by as much as 1.3% over the life of a filament in the ion source of the MS-10, proving that close control of the discrimination factor is essential for analytical precision with the instrument. These assertions are documented graphically with a compilation of data which represents more than two years experience with the method. We also report measurements of the mass discrimination of the MS-10 and its linearity with mass which indicate that the latter quantity is acceptable when the repeller voltage for the ion source is close to +1 V and is unacceptable otherwise. The spike material is available, upon request, to those laboratories which decide firmly to undertake further testing of the method.     

Chemical evolution of mid-ocean ridge hot springs

Chemical analyses yielding elemental concentrations of major and minor elements of four hot springs on the East Pacific Rise at 21°N and 10 hot springs from the southern trough of the Guaymas Basin, Gulf of California provide a basis for thermodynamic modeling of conductive cooling of the hydrothermal endmembers, mixing of the hydrothermal endmember with seawater, and reaction of an EPR-type fluid with sediment of bulk chemical composition corresponding to unaltered sediment from DSDP hole 477 in the Guaymas Basin. Results of the calculations indicate that conductive cooling of endmember fluids within closed chimneys and conduits accounts for the solution composition of one vent on the East Pacific Rise and several vents in Guaymas Basin. Mixing of the hydrothermal fluids with seawater yields a prediction of mineral assemblages closely approximating those observed in samples of chimneys from the East Pacific Rise and drill cores in Guaymas Basin. The hypothesis that Guaymas Basin hydrothermal fluids result from interaction of an EPR-type fluid with sediment cover in Guaymas Basin is supported by calculations which predict an increase in pH to a value similar to Guaymas Basin fluids, an order-of-magnitude decrease in metal concentrations, and an excellent agreement between predicted mineral assemblages as a function of extent of interaction with sediment, and observed mineral assemblage distribution with depth.     

Reviewing the discoverability and accessibility to data and information products linked to Essential Climate Variables

ABSTRACT

Essential Climate Variables (ECVs) are geophysical records generated from systematic Earth Observations associated with climate variations, changes, and impacts. ECVs products support the data and information needs of international frameworks and policies such as the work of the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC). We map the main networks and initiatives publishing ECVs, by presenting an overview of existing satellite-based ECVs, their general data creation characteristics, discoverability and accessibility methods from an end-user perspective. We investigate key initiatives providing or coordinating access to ECV data records, such as the Global Climate Observing System (GCOS), the Committee on Earth Observation Satellites (CEOS), the Coordination Group for Meteorological Satellites (CGMS), Joint Working Group on Climate (WGClimate), the Remote Sensing Systems (REMSS), and the European Space Agency Climate Change Initiative (ESA CCI). We find that ECV data discovery and access is difficult and time consuming due to the lack of common data and metadata catalogues. In addition, the selection of fit-for-purpose data records by end-users requires the implementation of interoperable standards and scalable data infrastructures to allow the generation of tailored applications and data-driven information products in support of decision-making processes.     

Potential implications of global warming and barrier island degradation on future hurricane inundation,property damages,and population impacted

Hurricane flooding is a leading natural threat to coastal communities. Recent evidence of sea level rise coupled with potential future global warming indicate that sea level rise will accelerate and hurricanes may intensify over the coming decades. In regions fronted by barrier islands, the protective capacity of these islands may diminish as they are degraded by rising sea level. Here we present a hydrodynamic and geospatial analysis of the relative role of barrier island degradation on potential future hurricane flooding. For the City of Corpus Christi, Texas, USA, hurricane flooding is projected to rise between 20% and 70% by the 2030s, resulting in an increase in property damages and impacted population. These findings indicate that adaptive management strategies should be developed and adopted for mitigating loss of natural barrier islands when these islands act as protective features for populated bayside communities. Finally, this study illustrates a method for applying models to forecast future storm protection benefits of barrier island restoration projects.     

Quaternary reactivation of a basement structure in the Barreirinhas Basin, Brazilian Equatorial Margin

The Pirapemas Lineament is a remarkable 200-km-long, NE-SW trending structure in the Barreirinhas Basin, one of the several Brazilian coastal basins. This lineament splits the study area in two sectors of distinctive morphology, drainage patterns, and sedimentary covers. Terrain northward of the lineament presents a smooth topography with sub-parallel to sub-dendritic drainage patterns, whereas a dissected plateau characterized by incised valleys and rectangular drainage pattern occurs southward, suggesting a structural control by joints and faults. Geological field data, crossed with thermal luminescence (TL) and optically stimulated luminescence (OSL) dating, revealed that the surface southward of the lineament consists mostly of Miocene and late Pleistocene sedimentary deposits, represented by the Barreiras Formation and the Post-Barreiras sediments, respectively. In contrast, relatively younger sands mantle most of the northward terrain, as indicated by well-preserved paleodune deposits that grade into active aeolian dunes of the Lençóis Maranhenses National Park. Geomorphological and geological data analysis suggests that the northern sector is under the effect of subsidence, proving that the Pirapemas Lineament is an active agent modeling the landscape in the region. Geophysical data (gravity and seismic) confirm that such a structural feature is the surface expression of an active deep-seated basement fault.     

Triassic stretching directions in Iberia and North Africa inferred from magnetic fabrics

During the Triassic, Iberia and western North Africa displayed a unique situation in relation with the Central and North Atlantic opening and westward expansion of the Tethys. Unravelling the stretching direction in Triassic deposits of the studied area can help in our understanding of this scenario. The tectonic setting is characterized by localized basins with strong thickness variations greatly influenced by previous post‐Variscan mechanical discontinuities. In this work, we revise and compile magnetic fabric data from eight Triassic depocentres in terms of defining the stretching direction (i.e. magnetic lineation), resulting from extensional deformation of this period. Data show the importance of the opening of the Atlantic rift as the leading process during the Triassic. Dextral transtension can explain the deflection of the extensional direction observed in most studied depocentres that is caused by the activity of previous major oblique faults.     

The management challenge posed by marine dispersal of terrestrial plants in coastal dune systems

Abstract:    Marine dispersal provides a mechanism for introduced plants to invade coastal systems. Regular surveillance is essential for management of marine dispersed weeds. This paper outlines the biological, physical and management dimensions of this coastal issue in New Zealand.