Geochemical characterization of recent sediments in the Baltic Sea by bulk and electron microprobe analysis     

Franois Belmans  Ren van Grieken  Lutz Brügmann 《Marine Chemistry》1993,42(3-4)

Nineteen samples of silty and clayey sediments of the Baltic Sea were analyzed by bulk methods (atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry), as well as by electron probe X-ray microanalysis (EPXMA). Processing of the EPXMA-data resulted in nine different particle types which have been identified as different mineral species. Quartz and aluminosilicate particles are most abundant (often more than 95%), although they are not of much help for the characterization of the geochemistry of Baltic sediments. Reduction products, such as Fe-sulfides and rhodochrosite, are found in anoxic sediment environments (e.g. Gotland Deep). The oxides/hydroxides of iron and manganese are more indicative of oxic environments (e.g. Kattegat). In regions with periodic changes in the redox conditions, oxides/hydroxides and sulfides are detected side by side (e.g. Lübeck Bight, Arkona Basin). The detected Ca- and Ti-rich particles show a geographical dependence. The Ca-rich particles are found in the transition region between the Baltic Sea and the North Sea. Ti-rich particles have high abundances around the coastlines of Germany (e.g. Lübeck Bight) and southern Poland. The results of the bulk analysis and of the individual particle analysis are often complementary.  相似文献   

Cultural-Genetic Aspects Of Bantu Urbanization In South Africa 1     

Lutz Holzner  Graham H. T. Hart 《The Professional geographer》1970,22(2):67-73

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IV. Stratigraphie Die fazielle Einstufung fossilführender Sedimente     

Hermann Schmidt  Karl Hoffmann  Erich Brand  Wolfgang Schott  Otto Seitz  Johannes Wolburg  Franz Bettenstaedt  F. E. Hecht  Hilmar Schumann  F. Heidorn 《International Journal of Earth Sciences》1948,35(2):175-178

Ohne Zusammenfassung  相似文献   

Similarity and regional differences in Quaternary arvicolid evolution in Central and Eastern Europe     

Lutz C. Maul  Anastasia K. Markova   《Quaternary International》2007,160(1):81

Because of their rapid evolution and abundant fossil record, arvicolid molars are commonly employed in Quaternary biostratigraphy. In addition, with their extensive geographical ranges these fossils often permit interregional faunal correlations. However, as a pre-condition for such correlations it has to be established that the occurrences are really time parallel in the different regions. This paper deals with the particular comparison of arvicolid records from Central and Eastern Europe. In most of the earliest and latest records of the species investigated similarities in the spectrum of accompanying species can be observed. In some cases endemism (Ungaromys, Ellobius, Eolagurus, Villanyia, several Pliomys species) or different taxonomic interpretations do not provide a sufficient base for comparison. Only for a few taxa can clear biostratigraphical differences of ranges be recognised (mainly Mimomys savini-Arvicola and various lineages within the genus Microtus). In some cases, differences in the chronostratigraphical ranges are possibly caused by the lack of a geological and palaeomagnetic framework for most of the Central European localities.  相似文献   

New insights into the history and origin of the southern Maya block,SE México: U–Pb–SHRIMP zircon geochronology from metamorphic rocks of the Chiapas massif     

Bodo Weber  Alexander Iriondo  Wayne R. Premo  Lutz Hecht  Peter Schaaf 《International Journal of Earth Sciences》2007,96(2):253-269

The histories of the pre-Mesozoic landmasses in southern México and their connections with Laurentia, Gondwana, and among themselves are crucial for the understanding of the Late Paleozoic assembly of Pangea. The Permian igneous and metamorphic rocks from the Chiapas massif as part of the southern Maya block, México, were dated by U–Pb zircon geochronology employing the SHRIMP (sensitive high resolution ion microprobe) facility at Stanford University. The Chiapas massif is composed of deformed granitoids and orthogneisses with inliers of metasedimentary rocks. SHRIMP data from an anatectic orthogneiss demonstrate that the Chiapas massif was part of a Permian (∼ 272 Ma) active continental margin established on the Pacific margin of Gondwana after the Ouachita orogeny. Latest Permian (252–254 Ma) medium- to high-grade metamorphism and deformation affected the entire Chiapas massif, resulting in anatexis and intrusion of syntectonic granitoids. This unique orogenic event is interpreted as the result of compression due to flat subduction and accretionary tectonics. SHRIMP data of zircon cores from a metapelite from the NE Chiapas massif yielded a single Grenvillian source for sediments. The majority of the zircon cores from a para-amphibolite from the SE part of the massif yielded either 1.0–1.2 or 1.4–1.5 Ga sources, indicating provenance from South American Sunsás and Rondonian-San Ignacio provinces.  相似文献   

The 8.2-ka abrupt climate change event in Brown's Lake, northeast Ohio     

Brian Lutz  Gregory Wiles  Joshua Michaels 《Quaternary Research》2007,67(2):292-296

Many Northern Hemisphere paleoclimatic records, including ice cores, speleothems, lake sediments, ocean cores and glacier chronologies, indicate an abrupt cooling event about 8200 cal yr BP. A new well-dated series of sediment cores taken from Brown's Lake, a kettle in Northeast Ohio, shows two closely spaced intervals of loess deposition during this time period. The source of loess is uncertain; however, it is likely from an abandoned drainage and former glacial lake basin located to the north of the stagnant ice topography that gave rise to the kettle lake. Strong visual stratigraphy, loss on ignition data and sediment grain size analyses dated with 3 AMS radiocarbon dates place the two intervals of loess deposition between 8950 and 8005 cal yr BP. The possibility of a two-phase abrupt climate change at this time is a finding that has been suggested in other research. This record adds detail to the spatial extent and timing as well as possible structure of the 8.2-ka abrupt climate change event.  相似文献   

Intercomparison of Two Hydroxyl Radical Measurement Techniques at the Atmosphere Simulation Chamber SAPHIR     

Eric Schlosser  Birger Bohn  Theo Brauers  Hans-Peter Dorn  Hendrik Fuchs  Rolf Häseler  Andreas Hofzumahaus  Frank Holland  Franz Rohrer  Lutz Olaf Rupp  Manfred Siese  Ralf Tillmann  Andreas Wahner 《Journal of Atmospheric Chemistry》2007,56(2):187-205

At the atmosphere simulation chamber SAPHIR in Jülich both Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS) are operational for the detection of OH radicals at tropospheric levels. The two different spectroscopic techniques were compared within the controlled environment of SAPHIR based on all simultaneous measurements acquired in 2003 (13 days). Hydroxyl radicals were scavenged by added CO during four of these days in order to experimentally check the calculated precisions at the detection limit. LIF measurements have a higher precision (σ= 0.88×10⁶ cm^–3) and better time resolution (Δt = 60 s), but the DOAS method (σ= 1.24×10⁶ cm^–3, Δt = 135 s) is regarded as primary standard for comparisons because of its good accuracy. A high correlation coefficient of r = 0.95 was found for the whole data set highlighting the advantage of using a simulation chamber. The data set consists of two groups. The first one includes 3 days, where the LIF measurements yield (1 – 2) ×10⁶ cm^–3 higher OH concentrations than observed by the DOAS instrument. The experimental conditions during these days are characterized by increased NO_x concentration and a small dynamic range in OH. Excellent agreement is found within the other group of 6 days. The regression to the combined data of this large group yields unity slope without a significant offset.  相似文献   

Geomechanical Models for Clastic Grain Packing     

Christian A. Hecht 《Pure and Applied Geophysics》2004,161(2):331-349

This study proposes a classification of sphere models for grain packing types of coarse grained clastic soft and hard rocks with special emphasis on Permocarboniferous red-beds. The classification covers the range of principal packing types and different cements. Random sphere packing models are derived from ideal symmetric packing models. The study comprises both homogeneous models with equal single grain properties and heterogeneous models with different single grain properties. For each packing type geomechanically relevant parameters like the packing density or coordination numbers are calculated and discussed. The models are correlated with results of image analysing and standard rock engineering experiments that were carried out on a variety of grain mixtures and sedimentary rocks of Permocarboniferous age. The discussion is concerned with the principles of grain packing models and the particular effects of distinct packing types on the petrophysical rock properties and the geomechanical behaviour of the examples presented.  相似文献   

Infrared reflection spectra,directional dispersion of the phonon modes and dynamical effective charges of FeS2-Marcasite     

H. D. Lutz  G. Wäschenbach 《Physics and Chemistry of Minerals》1985,12(3):155-160

The polarized far-infrared reflection spectra of single crystals of FeS₂-marcasite are presented in the range from 40–700 cm^?1. The spectra show 7 reststrahlen bands, as predicted by group theory. The oscillator parameters ?_{α ∞}, ω_{α f}, ?_{α f}, γ_{α f}, and the transversal and longitudinal optical phonon frequencies ω_TO and ω_LO as well as effective ionic charges and oscillator strength weighted mean phonon frequencies were calculated. The anisotropic behaviour of these quantities is discussed in relation to the data for FeS₂-pyrite. It is shown that the ionicity of marcasite is considerably smaller than that of pyrite, especially in the a and c direction. The directional dependence of the phonon frequencies is given and discussed with regard to the spectra of polycrystalline samples.  相似文献   

Note on the surface-to-geostrophic wind relationship from observations in the German Bight     

Lutz Hasse 《Boundary-Layer Meteorology》1974,6(1-2):197-201

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