Lithostratigraphy,sedimentation and evolution of the Volta Basin in Ghana     

John N. Carney  Colm J. Jordan  Christopher W. Thomas  Daniel J. Condon  Simon J. Kemp  John A. Duodo 《Precambrian Research》2010

We present a revised lithostratigraphy for the Voltaian Supergroup of Ghana, based on a review of existing literature, interpretations of remotely sensed data and reconnaissance field survey of the Volta Basin. These strata thicken eastwards, to a maximum of between 5 and 6 km adjacent to the Pan-African Dahomeyide orogen. They began to accumulate some time after about 1000 Ma, along the margin of an epicontinental sea. Initial sedimentation, comprising the age-equivalent Kwahu and Bombouaka Groups, shows a cyclical mode of deposition controlled by eustatic changes in sea-level that produced a range of nearshore marine, littoral and terrestrial environments.  相似文献   

Potential for deep geological sequestration of CO2 in Switzerland: a first appraisal     

Gabriel Chevalier  Larryn W. Diamond  Werner Leu 《Swiss Journal of Geoscience》2010,103(3):427-455

Possibilities to sequester anthropogenic CO₂ in deep geological formations are being investigated worldwide, but the potential within Switzerland has not yet been evaluated. This study presents a first-order appraisal based solely on geological criteria collated from the literature. The Swiss Molasse Basin (SMB) and the adjacent Folded Jura are the only realms of the country where CO₂ could conceivably be stored in saline aquifers. Evaluation of geological criteria at the basin-wide scale shows that the SMB–Jura has moderate potential (score of 0.6 on a scale from 0 to 1) when compared to basins elsewhere. At the intrabasinal scale, inspection of the stratigraphy reveals four regional candidate aquifers that are sealed by suitable caprocks: top Basement plus basal Mesozoic sandstones, all sealed by the Anhydrite Group; Upper Muschelkalk sealed by the Gipskeuper; Hauptrogenstein sealed by the Effinger Member, and Upper Malm plus Lower Cretaceous sealed by the Lower Freshwater Molasse. Nine geological criteria are defined to evaluate the storage potential of these and other smaller scale candidates. A numerical scoring and weighting scheme allows the criteria to be assessed simultaneously, permitting the storage potential to be depicted using the 0–1 scale in contoured maps. Approximately 5,000 km² of the central SMB exhibits potentials between 0.6 and 0.96. The Fribourg–Olten–Luzern area is the most favoured owing to the presence of several sealed aquifers within the preferred 800–2,500 m depth interval, and to its low seismicity, low geothermal gradient, low fault density, and long groundwater residence times. Smaller areas with good potential lie between Zürich and St. Gallen. In contrast, western Switzerland, the Jura and the southern SMB have markedly poorer potential. Considering only the portions of the aquifers with potential above 0.6, the theoretical, effective storage capacity of the basin is estimated to be 2,680 million tonnes of CO₂.  相似文献   

Analysis of overdeepened valleys using the digital elevation model of the bedrock surface of Northern Switzerland     

Peter Jordan 《Swiss Journal of Geoscience》2010,103(3):375-384

Based on surface and borehole information, together with pre-existing regional and local interpretations, a 7,150 square kilometre Raster Digital Elevation Model (DEM) of the bedrock surface of northern Switzerland was constructed using a 25 m cell size. This model represents a further important step in the understanding of Quaternary sediment distribution and is open to a broad field of application and analysis, including hydrogeological, geotechnical and geophysical studies as well as research in the field of Pleistocene landscape evolution. An analysis of the overdeepened valleys in the whole model area and, more specifically in the Reuss area, shows that, in most cases, overdeepening is restricted to the areas covered by the Last Glaciation Maximum (LGM). However, at various locations relatively narrow overdeepened valleys outreach the tongue basins and the LGM ice shield limits. Therefore, an earlier and further-reaching glacial event has probably contributed significantly to the overdeepening of these valleys. No significant overdeepening has been identified downstream of Böttstein (Aare) and Kaiserstuhl (Rhine), although the ice extended considerably further downstream, at least during the most extensive glaciation. Except for the bedrock between Brugg and Böttstein, no overdeepened valleys are found significantly north of the outcrop of Mesozoic limestone of the Folded and Tabular Jura. A detailed analysis of the Reuss area shows that the Lake and Suhre valleys are separated from the Emmen—Gisikon Reuss valley basin by a significant bedrock barrier. The individual bedrock valleys are divided into several sub-basins, indicating a multiphase evolution of the valleys. Some of the swells or barriers separating the sub-basins coincide with known late LGM retreat stages. In the Suhre valley, an old fluvial valley floor with restricted overdeepened sections is documented.  相似文献   

Navigating the dilemmas of climate policy in Europe: evidence from policy evaluation studies     

Constanze Haug  Tim Rayner  Andrew Jordan  Roger Hildingsson  Johannes Stripple  Suvi Monni  Dave Huitema  Eric Massey  Harro van Asselt  Frans Berkhout 《Climatic change》2010,101(3-4):427-445

Climate change is widely recognised as a ‘wicked’ policy problem. Agreeing and implementing governance responses is proving extremely difficult. Policy makers in many jurisdictions now emphasise their ambition to govern using the best available evidence. One obvious source of such evidence is the evaluations of the performance of existing policies. But to what extent do these evaluations provide insights into the difficult dilemmas that governors typically encounter? We address this question by reviewing the content of 262 evaluation studies of European climate policies in the light of six kinds of dilemma found in the governance literature. We are interested in what these studies say about the performance of European climate policies and in their capacity to inform evidence-based policy-making. We find that the evaluations do arrive at common findings: that climate change is framed as a problem of market and/or state failure; that voluntary measures tend to be ineffective; that market-based instruments tend to be regressive; that EU-level policies have driven climate policies in the latecomer EU Member States; and that lack of monitoring and weak enforcement are major obstacles to effective policy implementation. However, we also conclude that the evidence base these studies represent is surprisingly weak for such a high profile area. There is too little systematic climate policy evaluation work in the EU to support systematic evidence-based policy making. This reduces the scope for sound policy making in the short run and is a constraint to policy learning in the longer term.  相似文献   

Lines of OIV and SIV in the Goddard High-Resolution Spectrograph spectrum of RR Tel: constraints on atomic data     

G. M. Harper  C. Jordan  P. G. Judge  R. D. Robinson  K. G. Carpenter  T. Brage 《Monthly notices of the Royal Astronomical Society》1999,303(3):L41-L46

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Review of the systematics of CO₂–H₂O fluid inclusions     

Larryn W. Diamond   《Lithos》2001,55(1-4):69-99

Aqueous solutions that contain volatile (gas) components are one of the most important types of fluid in the Earth's crust. The record that such fluids have left in the form of fluid inclusions in minerals provides a wealth of insight into the geochemical and petrologic processes in which the fluids participated. This article reviews the systematics of CO₂–H₂O fluid inclusions as a starting point for interpreting the chemically more complex systems. The phase relations of the binary are described with respect to a qualitative P–T–X model, and isoplethic–isochoric paths through this model are used to explain the equilibrium and non-equilibrium behaviour of fluid inclusions during microthermometric heating and cooling. The P–T–X framework is then used to discuss the various modes of fluid inclusion entrapment, and how the resulting assemblage textures can be used to interpret the P–T conditions, phase states, and evolution paths of the parent solutions. Finally, quantitative methods are reviewed by which bulk molar volume and composition of CO₂–H₂O fluid inclusions can be determined from microthermometric observations of phase transitions.  相似文献   

Joint geodynamical and seismic modelling of the Eifel plume     

U. Wüllner  U. R. Christensen  M. Jordan 《Geophysical Journal International》2006,165(1):357-372

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Interbasin groundwater flow and groundwater interaction with surface water in a lowland rainforest, Costa Rica: A review     

David P. Genereux  Michael Jordan   《Journal of Hydrology》2006,320(3-4):385-399

This paper reviews work related to interbasin groundwater flow (naturally occurring groundwater flow beneath watershed topographic divides) into lowland rainforest watersheds at La Selva Biological Station in Costa Rica. Chemical mixing calculations (based on dissolved chloride) have shown that up to half the water in some streams and up to 84% of the water in some riparian seeps and wells is due to high-solute interbasin groundwater flow (IGF). The contribution is even greater for major ions; IGF accounts for well over 90% of the major ions at these sites. Proportions are highly variable both among watersheds and with elevation within the same watershed (there is greater influence of IGF at lower elevations). The large proportion of IGF found in water in some riparian wetlands suggests that IGF is largely responsible for maintaining these wetlands. δ¹⁸O data support the conclusions from the major ion data. Annual water and major ion budgets for two adjacent watersheds, one affected by IGF and the other not, showed that IGF accounted for two-thirds of the water input and 92–99% of the major ion input (depending on the major ion in question) to the former watershed. The large (in some cases, dominating) influence of IGF on watershed surface water quantity and quality has important implications for stream ecology and watershed management in this lowland rainforest. Because of its high phosphorus content, IGF increases a variety of ecological variables (algal growth rates, leaf decay rate, fungal biomass, invertebrate biomass, microbial respiration rates on leaves) in streams at La Selva. The significant rates of IGF at La Selva also suggest the importance of regional (as opposed to small-scale local) water resource planning that links lowland watersheds with regional groundwater. IGF is a relatively unexplored and potentially critical factor in the conservation of lowland rainforest.  相似文献   

Interval-valued random functions and the kriging of intervals   总被引：1，自引：0，他引：1  

Phil Diamond 《Mathematical Geology》1988,20(3):145-165

Estimation procedures using data that include some values known to lie within certain intervals are usually regarded as problems of constrained optimization. A different approach is used here. Intervals are treated as elements of a positive cone, obeying the arithmetic of interval analysis, and positive interval-valued random functions are discussed. A kriging formalism for interval-valued data is developed. It provides estimates that are themselves intervals. In this context, the condition that kriging weights be positive is seen to arise in a natural way. A numerical example is given, and the extension to universal kriging is sketched.  相似文献   

Dissolution kinetics of magnesite in acidic aqueous solution: a hydrothermal atomic force microscopy study assessing step kinetics and dissolution flux     

Steven R Higgins  Guntram Jordan  Carrick M Eggleston 《Geochimica et cosmochimica acta》2002,66(18):3201-3210

Magnesite (104) dissolution kinetics were studied in acidic aqueous solutions (2.0 < pH < 4.2) at temperatures between 60 and 90°C by atomic force microscopy (AFM). Comparison of dissolution fluxes obtained by AFM and chemical methods revealed six to seven times larger dissolution fluxes obtained by chemical analysis. Corresponding empirical activation energies were found to be 74 ±22 kJ/mol and 41 ± 4 kJ/mol (at pH 4.2) for the AFM and chemical methods, respectively. The empirical reaction order with respect to proton concentration was 0.36 ± 0.13 and 0.47 ± 0.03 for AFM and chemical methods, respectively. These comparisons suggest that the two experimental measurement methods differ as a result of the different sampling length scales associated with the methods. Negligible changes in step dissolution velocity with changes in bulk pH were found, suggesting that the principal source of increasing dissolution flux with decreasing pH is an increase in step density. However, the observed stable step orientation, which is dependent on pH, suggests that more than one proton adsorption equilibrium should be used to describe the surface chemistry of magnesite in acidic solution.  相似文献