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71.
72.
Alexandre Normandeau Jordan B. R. Eamer Pascal Bernatchez David Didier Patrick Lajeunesse Audrey Limoges Jean-Carlos Montero-Serrano 《Sedimentology》2023,70(1):100-120
Deltas are at the transition between fluvial and marine sedimentary environments where sediment density flows are often triggered during high river discharge events, forming submarine channels and sediment waves. On wave-influenced deltas, longshore currents are particularly efficient at transporting sediment alongshore, reducing the likelihood of sediment density flows from occurring at river mouths. This study describes four deltaic sedimentary systems at different stages of their evolution on a formerly glaciated continental inner shelf of eastern Canada in order to better understand the distribution of sediment density flows on wave-influenced deltas. Three types of settings are recognized as being prone to sediment density flows: (i) in the early stages of wave-influence and on large deltas, converging longshore currents can lead to offshelf sediment transport; (ii) on wave-influenced to wave-dominated deltas, a sandy spit can re-route the river mouth and sediment density flows form where the spit intersects the delta lip; (iii) in advanced stages of wave-dominated deltas and during their demise, rocky headlands are exposed and can intersect the slope, where off-shelf sediment transport occurs. These types of sediment density flows were all characterized by debris flows or surge-type turbidity currents which have limited offshore run-out. More rarely, hyperpycnal flows form at the river mouths, especially where the river incises glaciomarine clays prone to landsliding in the river, which increases fine-grained fluvial suspended sediment concentration. Overall, these results highlight the predominance of fluvial-dominated deltas during a phase of relative sea-level fall combined with high sediment supply. However, as soon as sediment supply diminishes, wave action remobilizes sediment alongshore modifying the distribution and types of sediment density flows occurring on wave-influenced deltas. 相似文献
73.
B. Christophe P. H. Andersen J. D. Anderson S. Asmar Ph. Bério O. Bertolami R. Bingham F. Bondu Ph. Bouyer S. Bremer J.-M. Courty H. Dittus B. Foulon P. Gil U. Johann J. F. Jordan B. Kent C. Lämmerzahl A. Lévy G. Métris O. Olsen J. Pàramos J. D. Prestage S. V. Progrebenko E. Rasel A. Rathke S. Reynaud B. Rievers E. Samain T. J. Sumner S. Theil P. Touboul S. Turyshev P. Vrancken P. Wolf N. Yu 《Experimental Astronomy》2009,23(2):529-547
The Solar System Odyssey mission uses modern-day high-precision experimental techniques to test the laws of fundamental physics
which determine dynamics in the solar system. It could lead to major discoveries by using demonstrated technologies and could
be flown within the Cosmic Vision time frame. The mission proposes to perform a set of precision gravitation experiments from
the vicinity of Earth to the outer Solar System. Its scientific objectives can be summarized as follows: (1) test of the gravity
force law in the Solar System up to and beyond the orbit of Saturn; (2) precise investigation of navigation anomalies at the
fly-bys; (3) measurement of Eddington’s parameter at occultations; (4) mapping of gravity field in the outer solar system
and study of the Kuiper belt. To this aim, the Odyssey mission is built up on a main spacecraft, designed to fly up to 13
AU, with the following components: (a) a high-precision accelerometer, with bias-rejection system, measuring the deviation
of the trajectory from the geodesics, that is also giving gravitational forces; (b) Ka-band transponders, as for Cassini,
for a precise range and Doppler measurement up to 13 AU, with additional VLBI equipment; (c) optional laser equipment, which
would allow one to improve the range and Doppler measurement, resulting in particular in an improved measurement (with respect
to Cassini) of the Eddington’s parameter. In this baseline concept, the main spacecraft is designed to operate beyond the
Saturn orbit, up to 13 AU. It experiences multiple planetary fly-bys at Earth, Mars or Venus, and Jupiter. The cruise and
fly-by phases allow the mission to achieve its baseline scientific objectives [(1) to (3) in the above list]. In addition
to this baseline concept, the Odyssey mission proposes the release of the Enigma radio-beacon at Saturn, allowing one to extend
the deep space gravity test up to at least 50 AU, while achieving the scientific objective of a mapping of gravity field in
the outer Solar System [(4) in the above list].
相似文献
74.
Bottled drinking water constitutes a significant part of total water consumption in developed countries and national and EU legislation regulates their market production. In the framework of an international project carried out by the EuroGeoSurveys Geochemistry Expert Group 36 bottled waters were obtained from public markets in Hungary in order to determine their hydrogeochemical composition. The objective of this study is to investigate the possible relationship between groundwater aquifer lithology and the processed and marketed bottled waters, and to develop a classification of bottled waters, based on their dissolved mineral content. Analytical results of this study are compared with the composition shown on bottle labels, and with archive hydrochemical data from the producing wells. Results show that, while processing of original groundwater, such as oxygen addition, iron or hydrogen-sulphide removal can significantly alter water composition, bottled water composition can be used for selection of sites for detailed hydrogeochemical and hydrogeological characterization. A simple and useful classification of bottled water quality is also presented that is based on natural groups of sampled waters derived by means of statistical data analysis methods. 相似文献
75.
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
76.
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
77.
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
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79.
80.
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