A Spatial Filtering Specification for an Auto-negative Binomial Model of Anopheles arabiensis Aquatic Habitats

This research accounts for spatial autocorrelation by including latent map pattern components as predictor variables in a malaria mosquito aquatic habitat model specification. The data used to derive the model was from a digitized grid-based algorithm, generated in an ArcInfo database, using QuickBird visible and near-infrared (NIR) data. The Feature Extraction (FX) Module in ENVI 4.4^® was used to categorize individual pixels of field sampled aquatic habitats into separate spectral classes, convert remotely sensed raster layers to vector coverages, and classify output layers to vector format as ESRI shapefiles. These data were used to construct a geographic weights matrix for evaluation of field and remote sampled covariates of Anopheles arabiensis aquatic habitats, a major vector of malaria in East Africa. The principal finding is that synthetic map pattern variables, which are eigenvectors computed for a geographic weights matrix, furnish an alternative way of capturing spatial dependency effects in the mean response term of a regression model. The spatial autocorrelation components suggest the presence of roughly 11 to 28% redundant information in the aquatic habitat larval count samples. The presence of redundant information in the models suggest that the sampling configuration of the An. arabiensis aquatic habitats, in the study sites, may cause field and remote observations of aquatic habitats to be dependent, rather than independent, moving data analysis away from the classical statistical independence model. A Poisson regression model, with a non-constant, gamma-distributed mean, can decompose field and remote sampled An. arabiensis data into positive and negative spatial autocorrelation eigenvectors, which can assess the precision of a malaria mosquito aquatic habitat map and the significance of all factors associated with larval abundance and distribution in a riceland agroecosystem.     

Can vein-filling speleothems constrain the timing of deep-seated gravitational slope deformation? A case study from the Vinschgau (Italian Alps)

The steep, south facing slopes of the central Vinschgau (Val Venosta, South Tyrol, northern Italy) are characterized by deep-seated compound rockslides affecting 51 km² and reaching beneath the Quaternary valley fill. Morphological features include double ridges, trenches, scarps, and counterscarps, whereby the extent of displacement rises from W to E. Near the toe of these slopes, abundant fractures are present whose orientation and spatial strongly suggest that they are related to the gravitational slope deformations. These fractures host carbonate speleothems which are associated with local tufa occurrences at the surface. Given that the metamorphic host rock is essentially carbonate-free, these carbonate deposits require extensive water-rock interactions to form. Modern springs along the toe of the slope are also mostly supersaturated with respect to calcite and locally also aragonite. The invariant chemical composition, very low tritium levels, and in particular the low oxygen isotope values indicate that this groundwater infiltrates at high elevation and is characterized by a long residence time. On the other hand, local infiltration in the lower reaches of the slope is very limited due to the semiarid climate and is incompatible with the measured groundwater stable isotope composition and the high degree of mineralization. We therefore propose a conceptual model which reconciles the deep-seated gravitational slope deformation with the occurrence of mineralized groundwater and associated carbonate precipitates in fractures near the toe of the slope. These deposits provide a means to place constraints on the timing of rock fracturing and hence the slope movements. U/Th dating of 34 samples from eight sites shows that speleothem deposition started 14.2 ka BP and occurred semi-continuously throughout the Holocene. Thus, gravitational displacements likely commenced with a lag of ~3–4 ka after the deglaciation of the valley, which is also consistent with the few available dates on the onset of other deep-seated slope deformations in the Alps.     

Reconstruction of Middle to Late Quaternary sea level using submerged speleothems from the northeastern Yucatán Peninsula

We examined 14 subaerially deposited speleothems retrieved from submerged caves in the northeastern Yucatán Peninsula (Mexico). These speleothems grew during the Middle to Late Quaternary and were dated by ²³⁰Th-U techniques to provide upper depth limits for past sea levels. We report the first relative sea-level limits for Marine Isotope Stages (MIS) 11 and 6, and present new evidence for sea-level oscillations during MIS 5 and early MIS 1. For the latter periods, the origin of growth interruptions is evaluated by combining petrographic methods with trace element analyses. The MIS 5c sea-level highstand probably occurred between 103.94 ± 0.58 ka and 96.82 ± 0.42 ka and must have exceeded -10.8 m (relative to present-day local sea level). The minimum average rate of sea-level fall over a 9.4 ka-long period during the MIS 5e/5d transition is calculated from stalagmite and published coral data at 1.74 ± 0.37 m/ka. For the early Holocene, previous discrepancies with respect to a potential multimetre oscillation of local sea level were found to be challenging to reconcile with the existing speleothem data from the area.     

High-resolution isotope records of early Holocene rapid climate change from two coeval stalagmites of Katerloch Cave,Austria

Two coeval stalagmites from Katerloch Cave show pronounced intervals of low δ¹⁸O values around 8.2, 9.1, and 10.0 kyr (all ages are reported before the year 2000 AD) and represent an inorganic U–Th dated climate archive from the southeast of the European Alps, a region where only very few well-dated climate records exist. The O isotope curves, providing near-annual resolution, allow a direct comparison to the Greenland ice core records, as temperature was the primary factor controlling the O isotopic composition of Katerloch speleothems.The 8.2 kyr climate anomaly lasted about one century, from 8196 to 8100 yr, with a maximum amplitude of 1.1‰ at 8175 yr. The event is characterized by a rapid onset and a more gradual demise and U–Th data as well as annual lamina counting support a rapid climate change towards cooler conditions within 10–20 yr. There is no strong evidence that the 8.2 kyr anomaly was superimposed on a pronounced longer-term cooling episode, nor do the new data support two separate cooling events within the 8.2 kyr event as reported by other studies. Our record also shows a distinct climate anomaly around 9.1 kyr, which lasted 70–110 yr and showed a maximum amplitude of 1.0‰, i.e. it had a similar duration and amplitude as the (central) 8.2 kyr event. Compared to the 8.2 kyr event, the 9.1 kyr anomaly shows a more symmetrical structure, but onset and demise still occurred within a few decades only. The different progression of the 8.2 (asymmetrical) and 9.1 kyr anomaly (symmetrical) suggests a fundamental difference in the trigger and/or the response of the climate system. Moreover, both stalagmites show evidence of a climate anomaly around 10.0 kyr, which was of comparable magnitude to the two subsequent events.Using a well constrained modern calibration between air temperature and δ¹⁸O of precipitation for the study area and cave monitoring data (confirming speleothem deposition in Katerloch reflecting cave air temperature), a maximum cooling by ca 3 °C can be inferred at 8.2 and 9.1 kyr, which is similar to other estimates, e.g., from Lake Ammersee north of the Alps. The O isotopic composition of meteoric precipitation, however, is a complex tracer of the hydrological cycle and these temperature estimates do not take into account additional effects such as changes in the source area or synoptic shifts. Apart from that, the relative thickness of the seasonally controlled lamina types in the Katerloch stalagmites remains rather constant across the intervals comprising the isotopic anomalies, i.e. the stalagmite petrography argues against major shifts in seasonality during the early Holocene climate excursions.     

Comparison and Combination of Coastal and Off-Shore Tide Gauge Measurements from Eivissa Island,Western Mediterranean

Two sea-level records, spanning eight months of simultaneous data in 2002, have been derived from pressure tide gauge measurements at Sant Antoni harbor (Eivissa Island, Western Mediterranean) and off Es Vedrà island, 15 km SW from Sant Antoni. The two time series are compared and used to characterize the sea-level variability in the Balearic Sea. The main forcings for the observed variations, astronomic tides, and meteorologic forcing by the inverse barometer effect are quantified. In a further step, an amplitude transfer function is determined, reflecting the frequency dependent amplification or damping of the nontidal sea-level residuals between both locations due to their local topography. The interpretation of the obtained transfer function indicates sea-level modulating topographic specifics not only for the coastal record at Sant Antoni, but also at the Es Vedrà site. In general, the application of such a transfer function allows the prediction of off-shore sea-level variations from coastal tide gauge measurements. In the present study, ellipsoidal sea-surface heights for Es Vedrà are inferred from Sant Antoni tide gauge data with an accuracy of about 1.5 cm by applying the determined transfer function and a geoid model.     

Comparison of Multimission Altimetric Sea-Surface Heights with Tide Gauge Observations in the Southern Baltic Sea

One possible technique to validate the observations of altimeter missions is the comparison with sea-surface heights measured by tide gauges. In our investigation, we compared observations of the two tide gauge stations, Sassnitz and Warnemünde, which are located at the southern coast of the Baltic Sea, with sea-surface heights obtained from the altimeter missions Geosat, ERS-1, ERS-2, and TOPEX/Poseidon. For this purpose, the compared sea-surface heights were related to a common reference system and extrapolated to a common location. GPS observations, leveling data, regional geoid information, sea-surface topography, and postglacial rebound were included in the analysis. Considering the uncertainties of all model components, a more reliable estimation of the error budget (source, type, and magnitude of the errors) was performed. The obtained absolute altimeter biases are (-243 - 32) mm for Geosat, (467 - 19) mm for ERS-1, (76 - 19) mm for ERS-2, and (13 - 18) mm for TOPEX.     

Carbonates in Upper Permian evaporites of the Northern Calcareous Alps,Austria

Thin black dolomites occur within the evaporitic Alpine Haselgebirge Formation (Late Permian) of the central and eastern Northern Calcareous Alps, Austria. They have been compared with the southalpine Bellerophon Formation byTollmann (1964). Samples obtained from the gypsum-anhydrite deposit of Wienern am Grundlsee, Styria, are mostly unfossiliferous mudstones (dolomicrite and dolomicrospar) devoid of sedimentary structures. Only few samples contain a low-diversity ostracode fauna. Electron microprobe and X-ray diffraction analysis indicate well-ordered and near-stoichiometric dolomite (49.9±0.2 mol% CaCO₃). The oxygen isotopic composition varies between –3.0 and –5.7 PDB. The ¹³C ratios fall into two distinct groups: –0.9 to +1.9, and –3.5 to –6.8 PDB. The carbon isotope data of the first group indicate a predominantly marine origin of the carbonates. The significantly depleted ¹³C ratios of the second group are probably due to freshwater influx into the basin and/or sulfate reduction. Sulfur and strontium isotope data from intercalated anhydrite and gypsum preclude an entirely non-marine origin of the brines. The light ¹⁸O ratios are probably due to early diagenetic sulfate reduction and/or dolomite recrystallization during moderate burial. A detailed interpretation of the depositional environment is rendered impossible because of the pervasive alpine tectonics. However, northalpine Bellerophon carbonates appear to be restricted to areas of major anhydrite deposition, and are absent in the halitedominated facies.

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Zusammenfassung Im zentralen und östlichen Abschnitt der Nördlichen Kalkalpen Österreichs treten geringmächtige, bituminöse Dolomite im Verband der salinaren Alpinen Haselgebirge Formation (Oberperm) auf. Sie wurden vonTollmann (1964) mit der südalpinen Bellerophon Formation verglichen. Bei den untersuchten Proben von der Gips- und Anhydritlagerstätte Wienern am Grundlsee (Steiermark) handelt es sich fast durchwegs um fossilleere Mikrite und Mikrosparite, die keinerlei Sedimentstrukturen aufweisen. Nur sehr wenige Proben führen Ostrakoden. Nach Mikrosonden-Analysen und röntgendiffraktometrischen Untersuchungen bestehen diese mikrokristallinen Dolomite aus fast stöchiometrischen, gut geordneten Dolomit (49.9±0.2 Mol% CaCO₃). Die Sauerstoffisotopenwerte schwanken von –3.0 bis –5.7 PDB und die ¹³C Verhältnisse fallen in zwei Gruppen: –0.9 bis +1.9, und –3.5 bis –6.8 PDB. Die Werte der ersten Gruppe indizieren eine im wesentlichen marine Bildung der Karbonate. Die deutlich leichteren ¹³C-Werte der zweiten Gruppe können durch Süßwassereinfluß während der Sedimentation und/oder durch Sulfatreduktion erklärt werden. Schwefel- und Strontium-Isotopenwerte, gemessen an Anhydriten und Gipsen im Verband mit den Dolomiten, schließen eine rein nicht-marine Herkunft der Salzlösungen aus. Die negativen ¹⁸O-Verhältnisse der Dolomite sind wahrscheinlich auf diagenetische Prozesse (Sulfatreduktion und/oder Umkristallisation) zurückzuführen. Die enorme alpidische Deformation dieser Evaporitserien gestattet es nicht, das ursprüngliche Ablagerungsmilieu der Karbonate zu rekonstruieren. Die nordalpinen Bellerophon Karbonate scheinen jedoch an Ablagerungsbereiche mit mächtiger Anhydritbildung gebunden zu sein, und fehlen primär in der Halit-dominierten Fazies.

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Résumé En Autriche, dans les secteurs central et oriental des Alpes calcaires du nord, existent des dolomies bitumineuses de faible puissance en relation avec la formation évaporitique alpine de l'Haselgebirge (Permien supérieur).Tollmann (1964) les a comparées à la formation sud-alpine de Bellérophon. Des échantillons provenant des gisements de gypse et d'anhydrite de Wienern sur le Grundlsee (Styrie) montrent des mudstones (dolomicrites à dolomicrosparites) dépourvus de fossiles et de structures sédimentaires. Seuls quelques échantillons contiennent une faune à ostracodes peu diversifiée. Les examens à la microsonde et aux rayons X montrent une dolomite bien ordonnée et quasi-stoechiométrique (49,9±0,2% moléculaire de CaCo₃). La composition isotopique de l'oxygène varie entre –3,0 et –5,7 PDB. Les rapports ¹³C se répartissent en deux groupes: –0,9 à +1,9 et –3,5 à –6,8 PDB. Ces données indiquent pour le premier groupe une origine surtout marine des carbonates. Les valeurs moins élevées des rapports du second groupe sont dues probablement à l'arrivée d'eau douce dans le bassin et/ou à une réduction des sulfates. Les valeurs isotopiques du soufre et du strontium, mesurées sur les gypses et anhydrites associés aux dolomies, excluent une origine entièrement continentale pour les saumures. Les faibles rapports ¹⁸O sont dûs probablement à une réduction diagénétique précoce des sulfates et/ou à la recristallisation de la dolomite pendant l'enfouissement. Une interprétation détaillée des conditions de dépôt est rendue impossible par l'ampleur de la déformation tectonique alpine. Il semble toutefois que des carbonates nord-alpins de type «Bellérophon» soient liés aux aires de forte sédimentation d'anhydrite et soient absents dans les faciès à halite dominante.

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Haselgebirge ( ) . Tollmann (1964) . , Grundlsee, , , - . . - , - , (49.9–0,2 % ₃). –3,0 –5,7% PDB, ¹³C : –0,9 –1,9% –3,5 –6,8% PDB. . / . , , , . ¹⁸ , , : / . . , , » « .

     

The Riga Dynamo Experiment

Cosmic magnetic fields, including the magnetic field of the Earth,are produced by the homogeneous dynamo effect in moving electricallyconducting fluids. We sketch the history of the underlying theoryand comment on previous attempts to realize homogeneous dynamos inthe laboratory. For the main part, we report on two series ofexperiments carried out at the Riga dynamo facility. In November1999 a slowly growing magnetic field eigenmode was observed forthe first time in a liquid metal experiment. In July 2000, themagnetic field saturation regime was studied and a number ofinteresting back-reaction effects were observed. A preliminaryinterpretation of the measured data is also presented.     

December 2004

Environmental Geology -