GPS network monitors the Western Alps' deformation over a five-year period: 1993–1998

  The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic problems still remain to be solved, such as the amount of N–S convergence in the Occidental Alps, the repartition of the deformation between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale GPS surveys of the Western Alps. More than 60 sites were surveyed in 1993 and 1998 with a minimum observation of 3 days at each site. GPS data processing has been done by three independent teams using different software. The different solutions have horizontal repeatabilities (N–E) of 4–7 mm in 1993 and 2–3 mm in 1998 and compare at the 3–5-mm level in position and 2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally smaller than 2 mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem to suggest that the N–S compression of the Western Alps is quite mild (less than 2 mm/yr) compared to the global convergence between the African and Eurasian plate (6 mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation of the Maghrebids and/or by rotations of Mediterranean microplates. Also, E–W velocity components analysis supports the idea that E–W extension exists, as already suggested by recent structural and seismotectonic data interpretation. Received: 27 November 2000 / Accepted: 17 September 2001     

A novel ozone sensor for direct eddy flux measurements

A small, lightweight (1.5 kg) and fast-response ozone sensor for direct eddy flux measurements has been built. The basis for detection is the chemiluminescence of an organic dye adsorbed on dry silica gel in the reaction with ozone. The chemiluminescence is monitored with a cheap and small blue-sensitive photomultiplier. At a flow rate of 100 l min^-1 the ozone sensor has a 90% response time of significantly better than 0.1 s with a detection limit lower than 50 ppt at S/N=3. There are no interferences from other atmospheric trace gases like NO_x, H₂O₂ and PAN. Water vapour and SO₂ enhance the chemiluminescence efficiency of the ozone sensor. Since their response times are 22 seconds and 30 minutes, respectively, no correlation between rapid ozone fluctuations and those of these two trace gases is noticed by the ozone sensor when operating at a frequency of 10 Hz.The ozone sensor was tested for several weeks in continuous measurements of ozone fluxes and deposition velocities over different croplands using the eddy correlation technique. Good agreement was found between ozone dry deposition velocities derived from profile measurements and by eddy correlation.     

Climate change in Yellowstone National Park: Is the drought-related risk of wildfires increasing?

The increased frequency of wildfires in the United States has become a common prediction associated with the build-up of greenhouse gases. In this investigation, variations in annual wildfire data in Yellowstone National Park are compared to variations in historical climate conditions for the area. Univariate and multivariate analytical techniques reveal that (a) summer temperatures in the Park are increasing, (b) January-June precipitation levels are decreasing, and (c) variations in burn area within the Park are significantly related to the observed variations in climate. Outputs from four different general circulation model simulations for 2 × CO₂ are included in the analyses; model predictions for increasing aridity in the Yellowstone Park area are generally in agreement with observed trends in the historical climate records.     

Stockwerktektonische Untersuchungen im Ruhrkarbon

Zusammenfassung Nach einer Erläuterung des Begriffes Stockwerktektonik wird über derartige Untersuchungen im südlichen Ruhrkarbon berichtet. Hier lassen sich drei durch fließende Übergänge verbundene tektonische Stockwerke unterscheiden: Das Flözleere ist durch das Vorherrschen tektonischer Formen niederer Größenordnung gekennzeichnet, die sich an bestimmten Stellen summieren. Das nächst höhere Stockwerk zeichnet sich durch eine sanfte Faltung und einige typische Faltenformen aus. Ein weiteres Stockwerk ist in seinem Formenschatz stärker differenziert. Über höhere Stockwerke liegen Untersuchungen vonKukuk, Kienow undSeidel vor. - Der vorliegende Bericht bringt nur Ergebnisse aus dem südlichen Revier; eine Gesamtdarstellung kann damit noch nicht gegeben werden.     

Computation of 5-day temperature normals in western Europe and the Mediterranean area

Summary UsingCraddock's method of representing the annual temperature variation by a two-term harmonic form fitted to monthly means, the harmonic coefficients of 63 stations in western Europe and around the Mediterranean Sea, as well as the 5-day normals for 24 Mediterranean stations, were computed and tabulated. In addition, some of the harmonic coefficients were charted and isoplethed, showing very distinctly the influence of continentality and topography. These charts, together withCraddock's charts for northern and northwestern Europe, provide fairly complete coverage of Europe and the Mediterranean area.This paper was prepared in the offices of the Technical Support Division of the 2d Weather Wing, United States Air Force, as a matter of routine business. The information contained herein was presented at the 5th Meeting of the Italian Society of Geophysics and Meteorology by Dr.Ingrid Weiss (Genoa: 23–25 April 1957). Since the paper is of general interest to all meteorologists of the Mediterranean area, it is published here with the permission of the originating agency as «Mémoire No. 3 du Centre International de Recherches sur la Météorologie de la Méditerranée (CIRMM)».     

Metallogenic provinces in South America

This paper discusses the broadscale distribution of some ore deposit types in South America, trying to discern possible relations with major geotectonic features. It does not cover all ore deposits but rather a selection based on available information, genetic types, geographic distribution, and a representation of deposit types which are either abundant or very rare in South America. Included are porphyry copper, zoned copper-zinc-lead-silver, contact-metasomatic, red-bed copper-uranium-vanadium, lead-zinc (including Mississippi Valley type), mercury, tin, pegmatite, carbonatite and alkalic complex, diamond, nickelcobalt-chromite-asbestos-talc, iron, bauxite, tungsten, titanium, uranium, gold, potash and phosphate deposits. Comparisons are made with the distribution of these deposit types in other continents, especially in North America and Africa. This leads to some speculations bearing on theories of ore genesis. The evidence suggests that upper crustal processes predominate in the formation of the majority of ore deposits considered (excepting carbonatites, alkalic complexes and diamond pipes). Also, the relative level of an orogenic belt exposed by erosion seems to be an important factor bearing on the presently known distribution of many ore deposit types. Furthermore, the fact that ore deposits of given types tend to be aligned along the Cordillera in more or less defined belts with changing chemical composition accross the Andes, which partake in all its inflections, and in patterns which are similar in North and South America, indicates that they are either dependent on the distribution of eugeosynclinal vs miogeosynclinal sediments in the original geosynclinal prism, or that their character is related to distance from the major batholitic masses or to shallow stocks and volcanic activity. The indicated correlation with sediment character and evaporites speaks in favor of modem concepts viewing hydrothermal fluids as mainly meteoric but heated and circulated largely by igneous activity. This study raises more questions than it can answer and calls attention to a number of problems requiring further research. From a practical point of view, this investigation reveals several possibilities for future exploration, as well as opportunities for further development of mineral resources in South America. Several countries could probably improve or diversify their mineral production significantly, thus raising the standard of living of their increasing population. Whereas in North America both Canada and the U.S.A. span from east to west the whole range of geological environments, from cratonic to geosynclinal and orogenic, in South America the distribución of countries is essentially either along the Cordillera or over shield areas, a fact of obvious geopolitical implications with regard to mineral resources.