Zum Auftreten von Sulfiden und ihrer Messung in situ im Breiten Luzin 1982 … 1984

An investigation is made into the seasonal and depth-related distribution of sulphides in the Breiter Luzin in the years of 1982 to 1984 with the aid of a white-lead line and of titration against copper sulphate. The results are discussed with respect to their importance for the occurrence of Coregonus albula and Mysis relicta. The occurrence of sulphides, which is different in the individual years with respect to concentration and distribution, is discussed concerning the possible causes of the annual differences in connection with air and water temperature, duration of sunshine and wind direction. A bathymetric and wind-exposure chart of the lake is presented for an assessment of the wind exposure.     

SENSOR: a tool for the simulation of hyperspectral remote sensing systems

The consistent end-to-end simulation of airborne and spaceborne earth remote sensing systems is an important task, and sometimes the only way for the adaptation and optimisation of a sensor and its observation conditions, the choice and test of algorithms for data processing, error estimation and the evaluation of the capabilities of the whole sensor system.The presented software simulator SENSOR (Software Environment for the Simulation of Optical Remote sensing systems) includes a full model of the sensor hardware, the observed scene, and the atmosphere in between. The simulator consists of three parts. The first part describes the geometrical relations between scene, sun, and the remote sensing system using a ray-tracing algorithm. The second part of the simulation environment considers the radiometry. It calculates the at-sensor radiance using a pre-calculated multidimensional lookup-table taking the atmospheric influence on the radiation into account. The third part consists of an optical and an electronic sensor model for the generation of digital images. Using SENSOR for an optimisation requires the additional application of task-specific data processing algorithms.The principle of the end-to-end-simulation approach is explained, all relevant concepts of SENSOR are discussed, and first examples of its use are given. The verification of SENSOR is demonstrated. This work is closely related to the Airborne PRISM Experiment (APEX), an airborne imaging spectrometer funded by the European Space Agency.     

Eruptive history and petrology of Mount Drum volcano,Wrangell Mountains,Alaska

Mount Drum is one of the youngest volcanoes in the subduction-related Wrangell volcanic field (80×200 km) of southcentral Alaska. It lies at the northwest end of a series of large, andesite-dominated shield volcanoes that show a northwesterly progression of age from 26 Ma near the Alaska-Yukon border to about 0.2 Ma at Mount Drum. The volcano was constructed between 750 and 250 ka during at least two cycles of cone building and ring-dome emplacement and was partially destroyed by violent explosive activity probably after 250 ka. Cone lavas range from basaltic andesite to dacite in composition; ring-domes are dacite to rhyolite. The last constructional activity occurred in the vicinity of Snider Peak, on the south flank of the volcano, where extensive dacite flows and a dacite dome erupted at about 250 ka. The climactic explosive eruption, that destroyed the top and a part of the south flank of the volcano, produced more than 7 km³ of proximal hot and cold avalanche deposits and distal mudflows. The Mount Drum rocks have medium-K, calc-alkaline affinities and are generally plagioclase phyric. Silica contents range from 55.8 to 74.0 wt%, with a compositional gap between 66.8 and 72.8 wt%. All the rocks are enriched in alkali elements and depleted in Ta relative to the LREE, typical of volcanic arc rocks, but have higher MgO contents at a given SiO₂, than typical orogenic medium-K andesites. Strontium-isotope ratios vary from 0.70292 to 0.70353. The compositional range of Mount Drum lavas is best explained by a combination of diverse parental magmas, magma mixing, and fractionation. The small, but significant, range in ⁸⁷Sr/⁸⁶Sr ratios in the basaltic andesites and the wide range of incompatible-element ratios exhibited by the basaltic andesites and andesites suggests the presence of compositionally diverse parent magmas. The lavas show abundant petrographic evidence of magma mixing, such as bimodal phenocryst size, resorbed phenocrysts, reaction rims, and disequilibrium mineral assemblages. In addition, some dacites and andesites contain Mg and Ni-rich olivines and/or have high MgO, Cr, Ni, Co, and Sc contents that are not in equilibrium with the host rock and indicate mixing between basalt or cumulate material and more evolved magmas. Incompatible element variations suggest that fractionation is responsible for some of the compositional range between basaltic andesite and dacite, but the rhyolites have K, Ba, Th, and Rb contents that are too low for the magmas to be generated by fractionation of the intermediate rocks. Limited Sr-isotope data support the possibility that the rhyolites may be partial melts of underlying volcanic rocks. Received March 13, 1993/Accepted September 10, 1993     

Diagenesis and Sr isotopic evolution of seawater using data from DSDP 590B and 575

New Sr isotopic and concentration analyses of bulk carbonate and porewaters from a carbonate-rich Miocene section sampled at DSDP Site 575 are reported and used, along with our earlier data from a section of similar age at DSDP Site 590B, in a numerical model to determine for each site the rate of Sr exchange during diagenesis and the degree to which this amount of exchange has shifted the⁸⁷Sr⁸⁶Sr of the bulk carbonate from the ratio each increment of sediment had when first deposited. Despite the fact that the two sites have very different water depth (4536 m at 575 vs. 1299 m at 590B), different sedimentation rate ( 10 m/My at 575 vs. 40 m/My at 590B), and significantly different porewater Sr²⁺ gradients, we find that the rate of Sr exchange as a function of sediment age is almost indistinguishable between the two sites. The rate of Sr exchange determined at the two sites is such that the resulting shift in bulk carbonate⁸⁷Sr⁸⁶Sr due to diagenesis is small compared to the total range of⁸⁷Sr⁸⁶Sr values measured, but large compared to the analytical uncertainty of the individual isotopic ratio measurements. By taking this shift into account we reconstruct the original⁸⁷Sr⁸⁶Sr of each increment of carbonate sampled, which when plotted as a function of age becomes our best estimate of the Sr isotopic evolution of seawater. Because Sr is very well mixed in the ocean, at any given time there is a single worldwide value of seawater⁸⁷Sr⁸⁶Sr. Therefore, if we are quantitatively accounting for the effect Sr exchange, we should find the same seawater evolution curve regardless of what DSDP Site is used. When we compare the observed bulk carbonate⁸⁷Sr⁸⁶Sr vs. age at the two sites they are seen to differ by amounts that are sometimes large compared to the analytical uncertainties of the measurements. However, when these data are corrected for the post-depositional Sr isotopic shifts predicted by our diagenetic model, we find almost perfect agreement. This agreement suggests that we have made a realistic determination of the rate of Sr exchange and its consequences in terms of shifting the⁸⁷Sr⁸⁶Sr of the bulk carbonate, and more importantly, that Sr isotopes can be used to correlate marine sediments with an accuracy comparable to the very small analytical uncertainties of modern isotopic measurements.     

Loughlinit (Na-Sepiolith) und Analcim in neogenen Sedimenten Anatoliens

Zusammenfassung Der Mineralbestand von Proben aus einem miozänen Tonhorizont der anatolischen Neogenformation bei Killik, Vilayet Eskiehir (Türkei), wird beschrieben und genetisch gedeutet. Hauptkomponenten bilden die Assoziationen Loughlinit-Analcim und Sepiolith-Analcim. Daneben sind Montmorillonit, Dolomit, Pyrit, Gips und — bei Anwesenheit von Loughlinit — wasserlösliche Na-Salze unbekannter Zusammensetzung vorhanden. Der Ton stellt das zweite bisher bekannte Loughlinitvorkommen dar. Analcim, Loughlinit und Sepiolith werden als diagenetische Bildungen im Sediment unter maßgeblicher Beteiligung Na- und Mg-reicher Porenwässer gedeutet. Die Möglichkeiten der Genese dieser Minerale werden durch Vergleich mit anderen Vorkommen und unter Berücksichtigung der geologischen Gegebenheiten diskutiert. Voraussetzung für die Bildung dieser Silikate ist ein enormes Na-Angebot aus einem eindampfenden Meeresbecken und/oder aus der Zersetzung sauren vulkanischen Materials und gleichzeitige Anlieferung von Mg, Al, Si in Form von Lösungen oder Detritus. Als wichtigste Liefergesteine werden die an den ehemaligen Beckenrändern verbreitet auftretenden Serpentinite betrachtet.

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The mineral content of specimens from a miocene clay horizon of the Anatolic Neogen formation near Killik, Vilayet Eskiehir (Turkey), has been described and a genetic interpretation has been given. The main components are the associations loughlinite-analcime and sepiolite-analcime. There are further montmorillonite, dolomite, pyrite, gypsum and watersoluble sodium salts of unknown composition, but the last ones apperently only if there is loughlinite. This clay is the second known occurrence of loughlinite. Analcime, loughlinite and sepiolite may have formed during diagenesis with an intensive interaction of sodium and magnesium rich pore solutions. The possibilities of the origin of these minerals have been discussed by comparing this occurrence with others and considering the geological environment.

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Frau Prof. Dr. D. Schachner danke ich für die Förderung der Arbeit und die Erlaubnis, die von der Deutschen Forschungsgemeinschaft zur Verfügung gestellte Röntgenapparatur benutzen zu können.     

Die tektonische Baugeschichte von Süd-Devonshire als Beispiel einer mehrphasigen variszischen Prägung

Five movement-phases during the Variscan tectogenesis shaped the structural cast of the Devonian rocks in South Devon. The first movement-phase, i. e. the main tectonic phase, resulted in the mappable fold system trending E-W or ENE-WSW in the west accompanied by related minor folds, and the first cleavage (s ₁) parallel to the axial planes. The cleavage planes dip to the south as far as the line Slapton-Bigbury, while farther to the south they dip to the north and finally to the south again, thus forming a huge fanning. In the second movement-phase a second cleavage (s ₂) with E-W strike associated with minor folds, was superimposed on the older structures south of the line Berry Head-Cornworthy. The trend of these folds is, more or less E-W. Furthermore the second cleavage shows a fanning which does not coincide with that of the first cleavage. South-vergent minor folds of bedding and cleavage planes, associated with small-scale southward thrusts represent structures of a third movement-phase. The fourth movement-phase was the kinking of mainly the first cleavage in the southern part of South Devon. There are two groups: one shows flat-lying kink-bands affecting mainlys ₁; seldoms ₂, and having a southward thrusting sense of movement while the other consists of nearly vertical kink-bands trending N-S which displace to the south on their eastern sides. Subsequently with the commencement of the New Red deposition, repeated tectonic stretching took place, resulting in N-S and WSW--ENE trending faults. The succession of the different tectonic events led to occasionally very complicated superimpositions. The rocks in the middle and southern part of South Devon suffered a regional metamorphosis that increases slowly towards the south. Finally, the tectonic structures of South Devon are compared with those in South Cornwall where the same movements-phases caused a completely different structural style.     

A computer-based system for processing geophysical data obtained from boreholes

A diverse set of computer programs has been developed at the Lawrence Livermore National Laboratory (LLNL)to process geophysical data obtained from boreholes. These programs support such services as digitizing analog records, reading and processing raw data, cataloging and storing processed data, retrieving selected data for analysis, and generating data plots on several different devices. A variety of geophysical data types are accommodated, including both wireline logs and laboratory analyses of downhole samples. Many processing tasks are handled by means of a single, flexible, general-purpose, data-manipulation program. Separate programs are available for processing data from density, gravity, velocity, and epithermal neutron logs. The computer-based storage and retrieval system, which has been in operation since 1973, currently contains over 4400 data files. Most of this data was obtained from the Nevada Test Site (NTS)in conjunction with the nuclear test program. Each data file contains a single geophysical parameter as a function of depth. Automatic storage and retrieval are facilitated by the assignment of unique file names that define the storage location of each data file. Files of interest to the user may be located and retrieved by means of a search program that examines the catalog. A convention recognized by all programs in the system is that of a zero ordinate denoting a gap in an otherwise continuous data trace. This convention provides a simple mechanism for editing and displaying data files in an automated and consistent manner.     

Relations between submarine fissures,internal breccias and mass flows during Triassic and earlier rifting periods

Deep fissures in shallow-water limestones filled with deep-water sediments are described from many places especially in the Triassic and Jurassic of the Tethys and in the Middle to Upper Devonian of the Variscian Mountains. Mass flows occur in the same formations and areas. On the island of Hydra (Greece) it was possible to show that both phenomena are linked by internal breccias of well-fitted limestone fragments. They are indicative of slope or near-slope positions and are very probably caused by flexure-like deformations of shallow-burial limestones. Seismic shocks producing overpressure may be instrumental in the disintegration of the semi-lithified limestones thus providing the material for mass flows. These events are associated with a tectonical subsidence as shown by deep-water matrix in the brecciated shallow-water limestones. They occur in areas and periods of submarine rifting, especially in late Devonian and Triassic time. At least four Triassic brecciation events can be traced from Greece to the Alps and correspond presumably to major transgressions in the cratonic basin of middle Europe.