Evolution microtectonique et paléo-champs de contraintes du Bassin de Vienne

Résumé

Une étude des structures cassantes permet de préciser l’évolution tectonique du Bassin de Vienne, généralement considéré comme un bassin de type « pull apart » typique. Le champ de contrainte ottnangien-carpathien (18,5-16, 5 Ma) est caractérisé par une compression NNW-SSE. Pendant le Badénien-Sannanticn (16,5-11 Ma) une zone cisaillante sénestre de direction NE-SW a été formée dans un régime en compression N-S et extension E-W. En liaison avec cette zone décrochante trois types d’extension locale conduisent à une forte subsidence dans les dépression : extension NE-SW parallèle aux accidents sénestres, extension E-W entre les décrochements et extension NW-SE au-dessus des zones décrochantes profondes. Le champ de contrainte vers la fin du Sannaticn est marqué par une compression ENE-WSW, tandis que celui du Pannonicn- récent est similaire á celui du Miocène moyen.

Une rotation de la paléocontrainte maximale horizontale, de NNW-SSE a ENE-SSW est mise en évidence pendant la période Ottnangien-Sannantien (18,5-11 Ma). Cette rotation est parallèle A celle des directions de mise en place des nappes carpathicnnes externes. L’origine des rotation est l’échappement continental des Alpes orientales et des Carpathes septentrionales vers le NE et son blocage graduel d’Ouest en Est au front des nappes carpathiennes. Après ce blocage, l’échappement a continué avec une faible intensité du Pannonien à l’Actuel. Alors que l’échappement a été initié par une compression N-S due á la collision Europe-promontoire Adriatique, le champ de contrainte à l’intérieur des blocs échappés reflète l’effet de leur blocage au front des nappes carpalhiques.     

Potential pollution of groundwater in the valley of the Seybouse River,north-eastern Algeria

In north-eastern Algeria, the Seybouse River is an important source of water used mainly for irrigation of large agricultural areas extending from the Guelma region to Annaba city. Industrial activities in this region contribute substantial water pollution to the river and the groundwater. Based on the different sources of pollution, mapping of areas vulnerable to groundwater pollution has been accomplished by combining land use and data on groundwater levels. The resulting maps show that the most vulnerable areas are those with large industrial activities—in Meboudja, Bouchegouf and Guelma. Infiltration and runoff contribute to pollution, and the highest infiltration rate is generally observed in areas of agricultural and industrial activities. Pollution of the aquifers in this area is of concern. Mountains, such as the Edough and Gelaat Bou Sbaa, contribute high runoff that carries pollutants towards the groundwater.     

An infrared spectroscopic and single-crystal X-ray study of malayaite, CaSnSiO5

Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO₅. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO₆ octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite. Received: 26 March 1998 / Revised, accepted: 23 December 1998     

The effects of soil type and chemical treatment on nickel speciation in refinery enriched soils: A multi-technique investigation

Aerial deposition of Ni from a refinery in Port Colborne, Ontario, Canada has resulted in the enrichment of 29 km² of land with Ni concentrations exceeding the Canadian Ministry of the Environment’s remedial action level of 200 mg kg⁻¹. Several studies on these soils have shown that making the soils calcareous was effective at reducing chemically extractable Ni, as well as alleviating Ni phytotoxicity symptoms in vegetable crops grown in the vicinity of the refinery. Conversely, dolomitic limestone additions resulted in increased uptake of Ni in the Ni hyperaccumulator Alyssum murale ‘Kotodesh’, a plant whose use was proposed as a remediation strategy for this area. In this paper we use multiple techniques to directly assess the role soil type and lime treatments play in altering the speciation of Ni in the Welland loam and Quarry muck soils around the refinery and relate these findings to Ni mobility and bioavailability.Stirred-flow dissolution experiments using pH 4 HNO₃ showed that Ni release from the limed Quarry muck and Welland loam soils was reduced (∼0.10%) relative to the unlimed soils (∼2.0%). Electron microprobe analysis (EMPA) identified approximately spherical NiO and Ni metal particles, which are associated with no other metals, and range from 5 to 50 μm in diameter. Synchrotron micro-X-ray absorption fine structure and X-ray fluorescence spectroscopies showed that Ni and Al layered double hydroxide (Ni-Al LDH) phases were present in both the limed and unlimed mineral soils, with a tendency towards more stable (e.g., aged-LDH and phyllosilicate) Ni species in the limed soil, possibly aided by the solubilization of Si with increasing pH. In the muck soils, Ni-organic complexes (namely fulvic acid) dominated the speciation in both limed and unlimed soils.The results reported herein show that both soil type and treatment have a pronounced effect on the speciation of Ni in the soils surrounding the Port Colborne refinery. We provide the first evidence that Ni-Al LDH phases can form in anthropogenically enriched mineral field soils at circumneutral pH, and can lead to a reduction in Ni mobility. In the organic soils Ni is strongly complexed by soil organic matter; a property enhanced with liming. Interestingly, increased accumulation of Ni by A. murale grown in the limed muck and loam soils indicates that the plant may be capable of removing Ni from those fractions typically considered unavailable to most plants.     

SPATIAL PATTERNS OF SUPPORT FOR A NUCLEAR WEAPONS FREEZE*

Support for a Freeze on nuclear weapons is greatest in the East with pockets of support in the Middle West and Pacific Coast States. Factors influencing the spatial pattern are Walker's innovativeness rankings, the number of peace/Freeze activist groups and the pattern of defense employment.     

Geological controls on Pleistocene glaciation and cirque form in Greece

Limestone and ophiolite rocks are common across the eastern Mediterranean and many of the highest mountains are formed in these rock types. In northwest Greece, Pleistocene glacial erosion was much more effective on limestone terrain where pronounced glacial incision and subglacial glacio-karst processes produced locally-complex topography. This enabled Pleistocene glaciers to form on a range of slope orientations in contrast to ophiolite terrains, where glaciers were strongly controlled by aspect. On limestone terrains, the largest ice masses formed on south-facing slopes, whereas in neighbouring higher mountains formed in ophiolite, glaciers were much more restricted and predominantly formed on north- and east-facing slopes.     

Reviews

OFFICE DEVELOPMENT: A Geographical Analysis by M. Bateman. 14 × 22 cm, xvi and 175 pages. Croom Helm: London 1985 (ISBN 0 7099 0697 8) $A35.95 (cloth).

ATLAS OF YOUTH UNEMPLOYMENT, 1981: The Geographic Distribution of Youth Unemployment in Australian Cities from the 1981 Census According to Birthplace and Gender by P. Matwijiw with E. Bamford and C. Maher. 21 × 29 cm, 127 pages. Australian Institute of Multicultural Affairs: Melbourne 1985 (ISBN 949890 33 2) $A12.00 (limp).

ENVIRONMENT AND HEALTH by A. J. Rowland and P. Cooper. 23 × 16 cm, vi and 205 pages. Edward Arnold: London 1983 (ISBN 0 7131 2855 0) $A27.95 (limp).

FAMINE AS A GEOGRAPHICAL PHENOMENON edited by B. Currey and G. Hugo. 17 × 24 cm, vi and 202 pages. Reidel: Dordrecht 1984 (ISBN 90 277 1762 1) Dfl 95.00, $US37.00 (cloth).

SOUTH AUSTRALIA'S CHANGING POPULATION (South Australian Geographical Papers No. 1) by G. J. Hugo. 25 × 18 cm, 71 pages. Royal Geographical Society of Australasia (SA Branch): Adelaide 1983 (ISBN 0 909112 05 03) $A4.00 (limp).

DEVELOPMENTS IN POLITICAL GEOGRAPHY edited by M. A. Busteed. 23 × 15 cm, 340 pages. Academic Press: London 1983 (ISBN 0 12 148420 3) $US42.00 (cloth).

NEITHER JUSTICE NOR REASON: A Legal and Anthropological Analysis of Aboriginal Land Rights by M. Gumbert. 22 × 14 cm, xv and 215 pages. University of Queensland Press: St Lucia 1984 (ISBN 0 7022 1746 8) $A20.00 (cloth).

RURAL RESOURCE MANAGEMENT by P. J. Cloke and C. C. Park. 14 × 22 cm, xiii and 473 pages. Croom Helm: London 1985 (ISBN 0 7099 2037 7) $A44.95 (cloth).

FARM POLICY IN AUSTRALIA by R. K. Hefford. 14 × 22 cm, xviii and 415 pages. University of Queensland Press: St Lucia 1985 (ISBN 0 7022 1698 4) $A40.00 (cloth).

TRANSPORT AND COMMUNICATIONS FOR PACIFIC MICROSTATES: Issues in Organisation and Management edited by C. C. Kissling. 14 × 21 cm, 192 pages. Institute of Pacific Studies, University of the South Pacific: Suva 1984. $A10.00 (cloth), $A8.00 (limp).

TIMES OF CRISIS: Epidemics in Sydney 1788–1900 by P. H. Curson. 15 × 25 cm, xii and 195 pages. Sydney University Press: Sydney 1985 (ISBN 0 424 00112 8). $A35.00 (cloth).

PEASANTS, SUBSISTENCE, ECOLOGY AND DEVELOPMENT IN THE HIGHLANDS OF PAPUA NEW GUINEA by L. S. Grossman. 24 × 16 cm, xxi and 302 pages. Princeton University Press: Princeton, NJ 1984 (ISBN 0 691 09406 3) $US45.50.

THE WORLD FOOD PROBLEM 1950–1980 by D. Grigg. 15 × 24 cm, 276 pages. Basil Blackwell: Oxford 1985 (ISBN 0 631 13481 6) $A58.50 (cloth).

POPULATION REDISTRIBUTION AND DEVELOPMENT IN SOUTH ASIA edited by L. A. Kosinski and K. M. Elahi. 17 × 24 cm, 243 pages. Reichel: Dordrecht 1985 (ISBN 90 277 1938 1) Dfl 120.00, $US44.00, £30.50 (cloth).

GEOGRAPHY AND ETHNIC PLURALISM edited by C. Clarke, D. Ley and C. Peach. 15 × 23 cm, xvii and 294 pages. Allen & Unwin: London 1984 (ISBN 0 04 309107 5) $A45.00 (cloth); (ISBN 0 04 309108 3) $A24.95 (limp).

SOCIAL GEOGRAPHY IN INTERNATIONAL PERSPECTIVE edited by J. Eyles. 14 × 22 cm, 295 pages. Croom Helm: London 1986 (ISBN 0 7099 0944 6) $A49.95 (cloth).

THE GENTRIFICATION OF INNER MELBOURNE: A Political Geography of Inner City Housing by W. S. Logan. 14 × 22 cm, xvi and 328 pages. University of Queensland Press: St. Lucia 1985 (ISBN 0 7022 1729 8) $A50.00 (cloth).

YELLOWCAKE AND CROCODILES: Town Planning, Government and Society in Northern Australia by J. Lea and R. Zehner. 14 × 22 cm, xxvi and 200 pages. Allen & Unwin: Sydney 1986 (ISBN 0 86861 875 6) $A24.95 (cloth); (ISBN 0 86861 843 8) $A 14.95 (limp).

THE BUNGALOW: The Production of a Global Culture by A. D. King. 20 × 25 cm, xii and 310 pages. Routledge & Kegan Paul: London 1984 (ISBN 0 7100 9538 4) $A62.50 (cloth).

THE WEST EUROPEAN CITY: A Social Geography by P. White. 15 × 23 cm, xviii and 269 pages. Longman: London 1984 (ISBN 0 582 30047 9) $A22.95 (limp).

THE SHAPING OF AMERICA: A Geographical Perspective on 500 years of History. Volume 1. Atlantic America, 1492–1800 by D. W. Meinig. 18 × 25 cm, xii and 500 pages. Yale University Press: New Haven 1986 (ISBN 0 300 03548 9) $US35.00 (cloth).

CANBERRA: MYTHS AND MODELS. Forces at Work in the Formation of the Australian Capital by K. F. Fischer. 21 × 30 cm, 166 pages. Institute of Asian Studies: Hamburg 1984 (ISBN 3 88910 009 0).

THE GEOGRAPHY OF PEACE AND WAR edited by D. Pepper and A. Jenkins. 15 × 23 cm, vi and 222 pages. Basil Blackwell: Oxford 1985 (ISBN 0 631 13559 6) $A75.00 (cloth); (ISBN 0 631 14069 7) $A23.95 (limp).

POLITICAL GEOGRAPHY: World‐economy, Nation‐state and Locality by P. J. Taylor. 15 × 23 cm, × and 238 pages. Longman: London 1985 (ISBN 0 582 30088 6) $A24.95 (limp).

THE INDUSTRIAL GEOGRAPHY OF CANADA by A. Blackbourn and R. G. Putnam 14 × 22 cm, 201 pages. Croom Helm: London 1984 (ISBN 0 7099 0622 6) $A42.50 (cloth).

THE FOODMAKERS by S. Sargent. 13 × 20 cm, 296 pages. Penguin: Ringwood 1985 (ISBN 0 14 007359 0) $A8.95 (limp).

LIMITS TO PREDICTION edited by R. B. McKern and G. C. Lowenthal. 13 × 19 cm, xiii and 163 pages. Australian Professional Publications: Sydney 1985 (ISBN 0 949416 029) $A14.95 (limp).

THE KANGAROO KEEPERS edited by H. J. Lavery. 18 × 25 cm, xxvi and 211 pages. University of Queensland Press: St Lucia 1985 (ISBN 0 7022 1875 8).

PRACTICAL ECOLOGY by D. D. Gilbertson, M. Kent and F. B. Pyatt. 15 × 23 cm, 320 pages, Hutchinson: London 1985 (ISBN 0 09 162651 X) £8.95.

BASIC BIOGEOGRAPHY (Second edition) by N. Pears. 15 × 24 cm, × and 358 pages. Longman: London 1985 (ISBN 0 582 30120 3) $A24.95 (limp).

ENVIRONMENTAL CHANGE (Second edition) by A. Goudie. 23 × 15 cm, xi and 258 pages. Oxford University Press: Oxford 1983 (ISBN 0 19 874135 9) A16.00 (limp).

MEGA‐GEOMORPHOLOGY edited by R. Gardner and H. Scoging. 16 × 24 cm, xiii and 240 pages. Oxford University Press: Oxford (ISBN 0 19 823244 6) $A48.00.

GRANITE LANDFORMS by C. R. Twidale. 25 × 17 cm, xxiii and 372 pages. Elsevier: Amsterdam 1982 (ISBN 0 444 42116 5) $A148.25.     

Neural networks and the separation of cosmic microwave background and astrophysical signals in sky maps

We implement an independent component analysis (ICA) algorithm to separate signals of different origin in sky maps at several frequencies. Owing to its self-organizing capability, it works without prior assumptions on either the frequency dependence or the angular power spectrum of the various signals; rather, it learns directly from the input data how to identify the statistically independent components, on the assumption that all but, at most, one of the components have non-Gaussian distributions.
We have applied the ICA algorithm to simulated patches of the sky at the four frequencies (30, 44, 70 and 100 GHz) used by the Low Frequency Instrument of the European Space Agency's Planck satellite. Simulations include the cosmic microwave background (CMB), the synchrotron and thermal dust emissions, and extragalactic radio sources. The effects of the angular response functions of the detectors and of instrumental noise have been ignored in this first exploratory study. The ICA algorithm reconstructs the spatial distribution of each component with rms errors of about 1 per cent for the CMB, and 10 per cent for the much weaker Galactic components. Radio sources are almost completely recovered down to a flux limit corresponding to ≃0.7 σ _CMB, where σ _CMB is the rms level of the CMB fluctuations. The signal recovered has equal quality on all scales larger than the pixel size. In addition, we show that for the strongest components (CMB and radio sources) the frequency scaling is recovered with per cent precision. Thus, algorithms of the type presented here appear to be very promising tools for component separation. On the other hand, we have been dealing here with a highly idealized situation. Work to include instrumental noise, the effect of different resolving powers at different frequencies and a more complete and realistic characterization of astrophysical foregrounds is in progress.     

The role of zinc-xanthate precipitation in sphalerite flotation

Flotation of sphalerite with ethyl, propyl, butyl, amyl, and hexyl xanthate is presented as a function of pH and concentration. Surface species have been identified with infrared spectroscopy and correlated with flotation and electrophoretic results. Flotation is postulated to be controlled by the formation and adsorption of bulk precipitated zinc xanthate on the alkyl chains of chemisorbed collector species.