The luminosity function of nearby galaxies (mitteilungen der universitätssternwarte zu jena nr. 147)

Using the catalogue of galaxies within 10 Mpc by Kraan-Korteweg and Tammann (1979) the local luminosity function of galaxies is derived. Possibly there exists a large population of faint elliptical systems being an important constituent in the Universe. From this luminosity function the local mass density Q = 5.1 · 10^-31 g cm^-3 = 0.11 Q_c was obtained.     

Younger Dryas to mid-Holocene environmental history of the lowlands of NW Transylvania, Romania

Pollen, micro-charcoal and total carbon analyses on sediments from the Turbuta palaeolake, in the Transylvanian Basin of NW Romania, reveal Younger Dryas to mid-Holocene environmental changes. The chronostratigraphy relies on AMS ¹⁴C measurements on organic matter and U/Th TIMS datings of snail shells. Results indicate the presence of Pinus and Betula open woodlands with small populations of Picea, Ulmus, Alnus and Salix before 12,000 cal yr BP. A fairly abrupt replacement of Pinus and Betula by Ulmus-dominated woodlands at ca. 11,900 cal. yr BP likely represents competition effects of vegetation driven by climate warming at the onset of the Holocene. By 11,000 cal yr BP, the woodlands were increasingly diverse and dense with the expansion of Quercus, Fraxinus and Tilia, the establishment of Corylus and the decline of upland herbaceous and shrubs taxa. The marked expansion of Quercus accompanied by Tilia between 10,500 and 8000 cal yr BP could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate. At 10,000 cal yr BP, Corylus spread across the region, and by 8000 cal yr BP it replaced Quercus as a dominant forest constituent, with only little representation of Picea abies. Carpinus became established around 5500 cal yr BP, but it was only a minor constituent in local woodlands until ca. 5000 cal yr BP. Results from this study also indicate that the woodlands in the lowlands of Turbuta were never closed.     

Drop dimensions in Cb-clouds and general meteorological circumstances

Summary During test flights over the North Sea with the Fokker Friendship several cloud spectra have been determined. Seven of them, related to cumulonimbus clouds show that the width of the droplet spectrum can be related to the speed of surface wind. The high correlations cannot be explained completely by the fact that marine condensation nuclei tend to grow with increasing wind. Obviously increased turbulence also plays a role.     

Geostatistical regionalization of glacial aquitard thickness in northwestern Germany, based on fuzzy kriging

In many instances hydrogeological parameters obtained by conventional methods for selected localities within an aquifer or an aquitard are not sufficient for adequate regionalization at the scale of the entire layer. Here, we demonstrate an application of the fuzzy kriging method in regionalization of hydrogeological data, in which the set of conventional, crisp values is supplemented by imprecise information subjectively estimated by an expert. It is believed that such an approach eventually may reflect the real-world conditions more closely than a traditional crisp-value approach, because the former does not impose exactness artificially on phenomena which are diffuse by their nature. Spatial interpolation was done for the thickness of one of the major aquitards (till and glaciolacustrine clay) in northwestern Germany. The dataset consists of 329 crisp values from boreholes supplemented by 172 imprecise values defined as fuzzy numbers. It is demonstrated that the reliability of regionalization was higher, compared to regionalization performed with the crisp dataset only. Fuzzy kriging was performed with FUZZEKS (Fuzzy Evaluation and Kriging System) developed at the Ecosystem Research Center at the University of Kiel.     

Paleoenvironmental evolution of the Paratethys in the Slovenian Basin during the Late Paleogene

Several sections from the uppermost Eocene and Oligocene of northern Slovenia have been investigated with respect to sedimentary facies, foraminiferal assemblages, stable isotopes, carbonate microfacies, and palynology. The main objective was to reconstruct the paleoenvironmental history of the Paleogene Paratethys in this region of the eastern Alpine realm. The sediments exhibit a transgressive succession beginning with conglomerates, sandstones, and mudstones of fluvial and lacustrine origin followed by carbonates and muddy marls indicating marine conditions. The foraminiferal faunal changes from brackish to shallow marine to deeper marine assemblages and the distribution of the palynofloras corroborate the sedimentological results. Microfacies analysis of the limestones shows a wide variation of shallow water, generally mud-rich facies dominated by coralline algae, foraminifera, and corals. Microfaunas adapted to low-oxygen conditions indicate temporal sluggish bottom-water circulation which can be associated with high fresh-water fluxes. These results are discussed as reflecting both the global sea-level rise during the Early Oligocene and the regional tectonic and climatic evolution.     

Towards the establishment of a reliable proxy for the reactive surface area of smectite

Reactive surface area is one of the key parameters for studying the kinetics of mineral dissolution. The common practice in experimental kinetics is to normalize the dissolution rate to the surface area measured by the BET method. The relationship between BET surface area and the reactive surface area is not trivial in minerals such as smectites, which possess both internal and external surface areas, and in which the dissolution is controlled by the chemical attack on the edge surface. The present study examines two proxies for the reactive surface area of the Clay Mineral Society reference smectite SAz-1: BET surface area and the edge surface area measured using AFM.Since smectites are very microporous, their BET surface area is strongly influenced by the degassing procedure. It is demonstrated that outgassing the smectite powder at 135°C in a 15 mL min⁻¹ N₂ gas flow for at least 24 hours minimizes contribution from micropores to less than 11% of the BET surface area.Following dissolution experiments in solutions with a low electrolyte concentration, the BET surface area increased from 34 ± 2 m² g⁻¹ in raw SAz-1 to 127 ± 13 m² g⁻¹ in SAz-1 sample recovered from dissolution experiments. This increase in BET surface area is explained by a decrease in the average size of the smectite aggregates, and by an increase in microporosity due to the depletion in the major interlayer cation, i.e., Ca²⁺. As the BET surface area of the raw smectite sample includes considerably less microporosity compared to the BET surface area of the smectite recovered from dissolution experiments, the former is a better approximation of the external surface area of the dried sample powder.AFM measurements show that there is no correlation between the specific external surface area of the sample and its specific edge surface area. This observation is explained by the platy morphology of the smectite particle in which the specific external surface area depends linearly on the height reciprocal, whereas the specific edge surface area is independent of the particles height and depends linearly on the sum of the reciprocals of the length of the axes. Therefore, there is no reason to expect a correlation between the BET and the edge surface area. Our results show that the edge surface area (4.9 ± 0.7 m² g⁻¹) of the smectite particles cannot be predicted based on its external surface area (136 ± 20 m² g⁻¹). Therefore, the BET surface area cannot serve as a proxy for the reactive surface area. We suggest using AFM measurements of the specific edge surface area as an alternative proxy for the reactive surface area of smectite.     

Climate impact of high northern vegetation: Late Miocene and present

The Late Miocene belongs to the late phase of the Cenozoic. Climate at that time was still warmer and more humid as compared to today, especially in the high latitudes. Corresponding to the climate situation, palaeobotanical evidences support that vegetation in the high northern latitudes changed significantly from the Late Miocene until today. To quantify the climate impact of this vegetation change, we analyse how vegetation in the high northern latitudes contribute to climate evolution. For that, we perform climate modelling sensitivity experiments for the present and for the Late Miocene (Tortonian, 11–7 Ma). For our present-day sensitivity experiment, we introduce the Tortonian vegetation in the high northern latitudes. For our Tortonian sensitivity experiment, we introduce the modern vegetation on the same grid cells. In the Tortonian and in the present, the modern vegetation leads to a strong cooling of the northern extratropics (up to −4°C). Nevertheless, the meridional heat transports remain nearly unchanged in both cases. In general, the vegetation impact on climate is similar in the Tortonian and in the present. However, some exceptions occur. Due to the Tethys Ocean in the Tortonian, temperatures decline only weakly in eastern Europe and western Asia. In the Tortonian climate, temperatures on the Sahara realm rise (up to +1.5°C), while the temperatures do not change remarkably in the present-day climate. This different behaviour is caused by a stronger and more sensitive hydrological cycle on the Sahara region during the Tortonian.     

Reconstructing palaeotemperatures for the Early and Middle Pleistocene using the mutual climatic range method based on plant fossils

A new approach is proposed to obtain quantitative temperature reconstructions from Early and Middle Pleistocene pollen and megafloral records. Utilizing the indicator species concept pioneered by Iversen (1944, Geologiska Föreningen Förhandlingar Stockholm 66, 463–483), the new methodology overcomes the problem of non-analogue plant communities by only taking into account the presence/absence of taxa rather than their relative abundances. Based on the present day thermal tolerances of the taxa from a fossil assemblage, the temperature interval in which all taxa from this assemblage can coexist is determined. A databank containing the climate tolerances of 85 taxa from European pollen records was established. To increase the temperature resolution of the method, procedures were developed to assess the most likely intervals for the actual temperatures within the calculated common thermospheres and the routine evaluation of the mean temperatures of the warmest and coldest months (MTW and MTC). After calibrating the approach on modern assemblages, it was applied to Tiglian and Holsteinian pollen sequences from Lieth (northern Germany) and Lac du Bourget (northern French Alps). For both records the method yields detailed temperature reconstructions of temperate and cold episodes. During the coldest episode of the Lieth section, the MTC may have been as low as −16°C. Corresponding MTW values range from 14.5 to 21°C, thus testifying to a strong continentality at that time. During the warmest period reconstructed for the Lieth section, the MTC was similar to the value as measured in the area today (1.5°C), whereas the MTW was probably higher than at present (20.1°C). For the coldest interval from the Lac du Bourget pollen sequence, the reconstructed MTC values reach a minimum of −15°C. Corresponding MTW values range from 15 to 22°C, again implying a strong continentality. For the warmest period our approach yields MTC values between −2 and 2°C and MTW values between 16.5 and 22°C. For both records, the resolution for the MTW and MTC reaches 1.5 and 2.5°C, respectively.     

Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblende barometer

The Al-in-hornblende barometer, which correlates Al^tot content of magmatic hornblende linearly with crystallization pressure of intrusion (Hammarstrom and Zen 1986), has been calibrated experimentally under water-saturated conditions at pressures of 2.5–13 kbar and temperatures of 700–655°C. Equilibration of the assemblage hornlende-biotite-plagioclase-orthoclasequartz-sphene-Fe-Ti-oxide-melt-vapor from a natural tonalite 15–20° above its wet solidus results in hornblende compositions which can be fit by the equation: P(±0.6 kbar) = –3.01 + 4.76 Al _hbl ^tot r ²=0.99, where Al^tot is the total Al content of hornblende in atoms per formula unit (apfu). Al^tot increase with pressure can be ascribed mainly to a tschermak-exchange ( ) accompanied by minor plagioclase-substitution ( ). This experimental calibration agrees well with empirical field calibrations, wherein pressures are estimated by contact-aureole barometry, confirming that contact-aureole pressures and pressures calculated by the Al-in-hornblende barometer are essentially identical. This calibration is also consistent with the previous experimental calibration by Johnson and Rutherford (1989b) which was accomplished at higher temperatures, stabilizing the required buffer assemblage by use of mixed H₂O-CO₂ fluids. The latter calibration yields higher Al^tot content in hornblendes at corresponding pressures, this can be ascribed to increased edenite-exchange ( ) at elevated temperatures. The comparison of both experimental calibrations shows the important influence of the fluid composition, which affects the solidus temperature, on equilibration of hornblende in the buffering phase assemblage.