Crustal thickening and crustal extension as controls on the evolution of the drainage network of the central Swiss Alps between 30  Ma and the present: constraints from the stratigraphy of the North Alpine Foreland Basin and the structural evolution of the Alps     

Fritz Schlunegger  Rudy Slingerl  & Albert Matter 《Basin Research》1998,10(2):197-212

The combined information about sedimentary petrography from the North Alpine Foreland Basin and structural geology from the Alps allows a qualitative reconstruction of the drainage network of the central Swiss Alps between 30 Ma and the present. This study suggests that crustal thickening and crustal thinning significantly controlled the location of the drainage divide. It also reveals the possible controls of crustal thickening/thinning on the change of the orientation of the drainage network from across-strike between 30 and 14 Ma to along-strike thereafter. Initial crustal thickening in the rear of the wedge is considered to have formed the drainage divide between north and south at 30 Ma. Because the location of crustal thickening shifted from east to west between ≈30–20 Ma, the catchment areas of the eastern dispersal systems reached further south than those of the western Alpine palaeorivers for the same time slice. Similarly, the same crustal dynamics appear to have controlled two phases of denudation that are reflected in the Molasse Basin by petrographic trends. Uplift in the rear of the wedge caused the Alpine palaeorivers to expand further southward. This is reflected in the foreland basin by increasing admixture of detritus from structurally higher units. However, tectonic quiescence in the rear of the wedge allowed the Alpine palaeorivers to cut down into the Alpine edifice, resulting in an increase of detritus from structurally lower units. Whereas uplift in the rear of the wedge was responsible for initiation of the Alpine drainage systems, underplating of the external massifs some 50 km further north is thought to have caused along-strike deviation of the major Alpine palaeorivers. Besides crustal thickening, extension in the rear of the wedge appears to have significantly controlled the evolution of the drainage network of the western Swiss Alps. Slip along the Simplon detachment fault exposed the core of the Lepontine dome, and caused a 50-km-northward shift of the drainage divide.  相似文献   

Sedimentary processes and trace metal contaminants in the buccaneer oil/gas field,northwestern gulf of Mexico     

Richard B. Wheeler  John B. Anderson  Rudy R. Schwarzer  Claudia L. Hokanson 《Environmental Geology》1980,3(3):163-175

Sediments are the ultimate sink for contaminants in the marine environment, and physical processes of sedimentation influence the distribution and accumulation of these contaminants. Evaluation of contaminant levels in sediments is one approach to assessing environmental impact; data interpretation depends on consideration of sediment texture and mineralogy, however, which profoundly influence chemical composition. In this study, comparison of potentially contaminated sediments from the production field with control populations was done only within the context of similar (as to texture and organic carbon and carbonate content) sample groups as determined by cluster analysis. Ba, Cd, and Sr are identified as contaminants. Supported by the identification of a well-crystallized expandable clay—possibly bentonite—drilling fluids are a potential source of Ba. Ba and Sr may be unnaturally high because of their abundance in discharged produced formation waters, but may also be naturally controlled by the unique faunal assemblage associated with the structures. Cd is probably derived from corrosion of the structures and assorted debris on the seafloor. In general, contamination is limited to an area within 100 m of the platforms. Furthermore, substantial erosion around platforms has probably effectively removed and dispersed the bulk of the contaminants introduced into the marine environment by the offshore exploration/production operations.  相似文献   

Investigation of the potential surface–groundwater relationship using automated base-flow separation techniques and recession curve analysis in Al Zerba region of Aleppo,Syria     

Rudy K. Abo  Broder J. Merkel 《Arabian Journal of Geosciences》2015,8(12):10543-10563

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Sedimentology,three‐dimensional geobody reconstruction and carbon dioxide origin of Pleistocene travertine deposits in the Ballık area (south‐west Turkey)          下载免费PDF全文

Hannes Claes  Jeroen Soete  Koen Van Noten  Hamdy El Desouky  Marcelle Marques Erthal  Frank Vanhaecke  Mehmet Özkul  Rudy Swennen 《Sedimentology》2015,62(5):1408-1445

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From field study to numerical modeling of hydrothermal dolomitization in Early Cretaceous platform carbonates (Cantabrian mountains,northern Spain)     

F.H. Nader  C. Dumont  M.M. Shah  D. Garcia  R. Swennen  J.-M. Daniel  O. Lerat  B. Doligez 《Journal of Geochemical Exploration》2009

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Fluid flow reconstruction in the Sicilian Fold and Thrust Belt     

B. Dewever  R. Swennen 《Journal of Geochemical Exploration》2009

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Zn, Pb, Cu and As distribution patterns in overbank and medium-order stream sediment samples: their use in exploration and environmental geochemistry     

R. Swennen  J. Van der Sluys 《Journal of Geochemical Exploration》1998,65(1):27-45

Overbank and medium-order stream sediment samples were collected in Belgium and Luxembourg from 66 sampling locations (area of about 33,000 km²) and analysed for major and trace elements among which Zn, Pb, Cu and As. At each sampling location large bulk samples were taken, namely in the lower (normally at ≥1.5 m depth, over an interval of about 20–40 cm) and upper (normally upper 5–25 cm) parts of the overbank profiles and from the stream sediments. Furthermore, at a number of these sites, a detailed geochemical analysis of vertical overbank sediment profiles (sampling intervals of 10–20 cm) was subsequently carried out to unravel element variations through time and to help in the overall evaluation. For most sampled sections evidences such as ¹⁴C-dating and the absence of anthropogenic particles point towards a pre-industrial and often pristine origin of the lower overbank sediment samples. From the latter bulk samples, mean background concentrations were deduced. They reveal the existence of significant differences between the northern and southern part of Belgium (incl. Luxembourg) which relate to the difference in geological substrate. In the north dominantly non-lithified Quaternary and Tertiary sands, marls and clays occur while in the south Palaeozoic sandstones, shales and carbonate rocks outcrop. Consequently separate mean background values were calculated for the two areas. In the southern study area, some anomalous metal concentrations have been recorded in pre-industrial sediments. They are derived from mineralised Palaeozoic rocks, a feature which could be of interest for base metal exploration. In the upper overbank and stream sediments, in general, higher heavy metal and As contents were recorded with highest values in areas with metal mining, metal melting and cokes treatment industries. By comparing the trace element concentrations of the upper overbank or stream sediment samples with the concentrations detected in the lower overbank samples at each of the sampling locations, and by evaluating the vertical distribution patterns where available, the degree of pollution of the alluvial plain and the present-day stream sediments can be assessed. From this exercise, it is clear that highest pollution occurs in the northern part of Belgium, which relates to its high population density and industrial development.  相似文献   

ANC,BNC and mobilization of Cr from polluted sediments in function of pH changes     

A. Shtiza  R. Swennen  V. Cappuyns  A. Tashko 《Environmental Geology》2009,56(8):1663-1678

During the manufacturing of chromate salts (1972–1992) large quantities of Chromite Ore Processing Residue (COPR) were released into a decantation pond east of the former chemical plant of Porto-Romano (Durres, Albania), giving rise to yellow colored pond sediments. These Cr(VI) bearing sediments were deposited upon Quaternary silty-clay lagoonal sediments rich in iron oxides and organic matter. The pH values in these lagoonal sediments vary around 6.6, while in the pond sediments, it is mainly acidic (due to the presence of the sulfur stock piles in the area and the release of the H₂SO₄ from the activity of the former chemical plant), varying between 1.4 and 3.8. Continuous leaching of the COPR waste resulted in yellow-colored surface water runoff. The prediction of pH changes in the different types of sediments based upon acid/base neutralizing capacity (ANC/BNC) jointly with the quantitative data on release of heavy metals and especially Cr is considered an important advantage of the pH_stat leaching test if compared to conventional leaching procedures. Thus, factors controlling the leaching of Cr(VI), Cr(III), Ca, Al, Fe, Mg from the COPR were investigated by means of pH_stat batch leaching tests and mineralogical analysis. Moreover, mathematical and geochemical modeling complemented the study. The COPR in the area contain very high concentrations of chromium 24,409 mg/kg, which mainly occurs as Cr(III) (75–90%) as well as Cr(VI) (25–10%). The leaching of Cr(VI) occurs in all the range (2–10) of the tested pH values, however, it decreases under acidic conditions. Beside some reduction of Cr(VI) to Cr(III), the Cr(VI) content of the leachtes remains relatively high in the acidic environment, while the limning of Cr(VI) pond sediments will increase the release of the latter specie. The leaching of the Cr(III) occurs strictly under acidic conditions, whereby limning of these sediments will give rise to the lower solubility of Cr(III). The key mineral phases responsible for the fast release of the Cr(VI) are: the chromate salts (i.e. sodium chromate and sodium dichromate), while sparingly soluble chromatite (CaCrO₄) and hashemite (BaCrO₄) release Cr(VI) very slowly. Thus, pH and mineral solubility have been identified as key factors in the retention and the release of the hexavalent CrO₄ ²⁻ and Cr₂O₇ ⁻ from the COPR-rich pond sediments.  相似文献   

Structure and nuclear density distribution in the cheralite—CaTh(PO4)2: studies of its behaviour under high pressure (36?GPa)     

Philippe E. Raison  Stephen Heathman  Gilles Wallez  Carmen E. Zvoriste  Denis Bykov  Ga?l Ménard  Emmanuelle Suard  Karin Popa  Nicolas Dacheux  Rudy J. M. Konings  Roberto Caciuffo 《Physics and Chemistry of Minerals》2012,39(8):685-692

The crystal structure of the cheralite—CaTh(PO₄)₂—has been revisited by neutron diffraction and its behaviour under high pressure investigated by X-ray diffraction up to 36?GPa. The neutron diffraction data at ambient pressure gave a more accurate determination of the Ca/Th cation position than previous XRD data, taking advantage that the neutron scattering lengths of calcium and thorium are of same order of magnitude. The nuclear density distribution was also determined using the maximum entropy method (MEM) confirming that the two cations are not located at the same position in the unit cell but are slightly displaced from one another along a specific direction in order to minimize the electrostatic repulsion with the surrounding phosphorus atoms. At high pressure, the compound did not show any phase transition or amorphization. From the evolution of the unit-cell volume as a function of the pressure, the zero-pressure bulk modulus B₀ and its pressure derivative B₀ ^′ have been determined by fitting the experimental compressibility curve to the Birch–Murnaghan equation of state. The results are B₀?=?140(2) GPa and B ₀ ^′ ?=?4.4(4) GPa.  相似文献   

The role of international environmental instruments in enhancing transboundary marine protected areas: An approach in East Africa     

José Guerreiro  Aldo Chircop  David Dzidzornu  Catarina Grilo  Raquel Ribeiro  Rudy van der Elst  Ana Viras 《Marine Policy》2011

The increasing degradation of marine ecosystems has led to multiple calls for greater protection through the establishment of marine protected areas (MPAs). If created at the ecosystem or ecoregion level, MPAs will likely straddle maritime boundaries and therefore necessitate international cooperation. International environmental law and international law of the sea may facilitate cooperation between States in creating transboundary MPAs. The extent to which this body of law is actually or potentially useful for the establishment of transboundary MPAs is examined in the context of the East African Marine Ecoregion, focusing on Mozambique, South Africa, and Tanzania. A general survey and assessment of the applicable global, regional, and bilateral instruments in relation to the three States is conducted. Although some global instruments are relevant in the East African context, regional and bilateral instruments are more conducive to the establishment of transboundary MPAs. The article concludes that although a trilateral agreement between Mozambique, South Africa, and Tanzania would be an ideal vehicle for the establishment of a transboundary network of MPAs addressing both national and ecoregional conservation interests, a separate solution at each border will be the first step towards this goal.  相似文献