ALBERT

Description: Vertical phytoplankton distribution, temperol fluctuations and sedimentation rates were studied in the central Baltic Sea during the "Baltic Sea Patchiness Experiment 1986" (PEX'86). Vertical particle flux was measured with free sediment traps deployed at 30 and 60m depth for ten April/May 1986 within the PEX grid (20 x 40 nautical drifting days in miles). In the vicinity of one drifting trap water samples were collected in 10-12 depths down to 70m and vertical profiles of temperature, salinity, beam attenuation and light intensity were measured at three hour intervals. Water samples were analyzed for Chl.a, POC and PON content, dry weight and nutrients. Particulate parameters including the activity of 137 Cs were measured in trap samples. Suspended and sedimented particulates were counted under an inverted microscope. Precision and accuracy of the microscopical counts are discussed and confidence limits are calculated for different spec1es and applied counting schemes. Errors in all cases were smaller than the observed in situ variability. A general description of spring blooms in the central Baltic is given and the particular situation of spring 1986 is summarized. Within the station grid of PEX'86 an anticyclonic eddy was observed in which this study was conducted. Here the phytoplankton had reached peak concentrations and mass sedimentation of diatoms was about to start. The bloom was dominated by Thalassiosira levanderi and Chaetoceros spp. (lOµm size). Achnantes taeniata, Mesodinium rubrum, Gonyaulax catenata and an autotrophic Gymnodinium species (26-30µm) were also abundant. Horizontal patchiness and advection caused greater variability in the distribution of phytoplankton biomass blooms as well as temperature and attenuation during the first days than during the latter half of the investigation period. In four different areas within the PEX grid different developed independently. On still smaller time and space scales, the phytoplankton species composition also changed. The degree of patchiness was different for different species. General concepts explaining vertical distribution patterns of phytoplankton by physical and biological mechanisms are discussed. The species-specific distribution of selected diatoms, dinoflagellates and of the funktionally autotrophic ciliate M.rubrum are described. None of the species were homogeneously distributed although no vertical density stratification was observed. Whereas the diatoms and M.rubrum were present within the whole trophogenic layer, the dinoflagellates were only found in the upper 30m. The vertical distribution was different for concentrations were encountered each at species and different maximum depths respectively. Mechanisms affecting species-specific distribution of mobile and non-mobile phytoplankters in isopycnal layers are discussed in light of the particular situation of this study. Diurnal vertical migration is shown for two dinoflagellates and the phytociliate and triggering factors are discussed. All three species migrated upwards during the day and downwards at night. In its detail, however, the migratory behaviour differed between species and also within single populations. Different strategies of adaptation of phytoplankton to changing environmental conditions are suggested: Wheras diatoms adapt to fluctuations of the light climate by physiological adaptations, mobile organisms have the possibility to stay in an isolume layer. The significance of turbulence, of chainformation and of resting stages in the life cycles of phytoplankton is also evaluated. Trap deployments reveiled that only T.levanderi and Chaetoceros spp. sedimented. Their daily relative sedimentation rates (losses as % of standing stocks) increased over time and were species-specific (for T.levanderi max. 50%). Since part of the T.levanderi population was actively dividing (20% of the standing stock was found as paired cells) their suspended concentration decreased slower than that of Chaetoceros spp., although the daily sedimentation of the latter species was only about 30% of the standing stock. T.levanderi occured in chains in the water column but only single cells were found in sedimented material and paired cells were never found in the trap samples. Chaetoceros spores were rare in the water column and only sporadically collected by the sediment traps. The relative sedimentation rate of all other species was less than 5% per day. The settling velocity of the cells was estimated in different independent ways to be about 40-60m/d. This high sinking speed was attributed to aggregate formation. The results indicate that aggregate formation is not only species-specific but also differs between life-stages within one species. Variability of sedimentation rates on a timescale of hours was high, suggesting a diurnal pattern. Sedimentation did not change the vertical distribution patterns, indicating that cells were sinking with similar rates from all depths. The advantages of a Lagrangian sampling strategy (time series measurements 1n the vicinity of a free drifting buoy) for investigating phytoplankton development in time are evaluated and compared to a sampling at a moored station (Eulerian approach). In an environment that exhibits an intense patchiness even at spatial scales of lOOm, as encountered in this study, the influence of advection and patchiness on a time-series with a resolution of hours to days can not be neglected even if the Lagrangian approach is followed. Furthermore, in this study the variability of var1ous parameters measured in an Eulerian mode was not generally higher than that following the Lagrangian one, as one would have expected.

Description: The Owen Ridge south of Oman represents oceanic crust that was uplifted by compressional tectonic forces in the early Miocene. Build-out of the Indus Fan led to deposition of a thick sequence of turbidites over the site of the Ridge during the late Oligocene and early Miocene. Early Miocene uplift of the Ridge led to a pelagic cap of nannofossil chalks. Two short sequences of turbidites from the pre- and syn-uplift phases were chosen for detailed grain size analysis. The upper Oligocene section at Site 731 is composed of thin (centimeter-decimeter scale) graded mud turbidites separated by relatively thick (decimeter-meter scale) intervals of homogeneous, non-bioturbated clayey siltstones. These finer intervals are unusually silt-rich (about 60%) for ungraded material and were probably deposited as undifferentiated muds from a series of turbidity current tails. By contrast, the lower Miocene section at Site 722 is comprised of a sequence of interbedded turbidites and hemipelagic carbonates. Sharp-based silt turbidites are overlain by burrow-mottled marly nannofossil chalks. The Oligocene sequence may have accumulated in an overbank setting on the middle fan - the local topographic position favoring frequent deposition from turbidity current tails and occasional deposition from the body of a turbidity flow. Uplift of the Ridge in the early Miocene led to pelagic carbonate deposition interrupted only by turbidity currents capable of overcoming a topographic barrier. Further uplift eventually led to entirely pelagic carbonate deposition.

Description: Recent studies of abyssal peridotites (Johnson et al., 1990, doi:10.1029/JB095iB03p02661), mid-ocean-ridge basalts (MORBs) (McKenzie, 1985, doi:10.1016/0012-821X(85)90001-9) and their entrained melt inclusions (Sobolev and Shimizu, 1993, doi:10.1038/363151a0; Humler and Whitechurch, 1988, doi:10.1016/0012-821X(88)90055-6) have shown that fractional melting of the upwelling sub-oceanic mantle produces magmas with a much wider range of compositions than erupted MORBs. In particular, it seems that strongly depleted primary magmas are routinely produced by melting beneath ridges (Johnson et al., 1990, doi:10.1029/JB095iB03p02661). The absence of strongly depleted melts as erupted lavas prompts the question of how long such magmas survive beneath ridges, before their distinctive compositions are concealed by mixing with more enriched magmas. Here we report mineral compositions from a unique suite of oceanic cumulates recovered from DSDP Site 334 (Aumento et al., doi:10.2973/dsdp.proc.37.1977), which indicate that the rocks crystallized from basaltic liquids that were strongly depleted in Na, Ti, Zr, Y, Sr and rare-earth elements relative to any erupted MORB. It thus appears that the magmatic plumbing system beneath the Mid-Atlantic Ridge permitted strongly depleted magmas to accumulate in a magma chamber and remain sufficiently isolated to produce cumulate rocks. Even so, spatial heterogeneity in the compositions of high-calcium pyroxenes suggests that in the later stages of solidification these rocks reacted with infiltrating enriched basaltic liquids.

Description: Ziel dieser Arbeit war es am Beispiel zweier Schleswig-Holsteinischer Marschsedimente die Veränderungen des gestaltlichen Porengefüges bei geostatischer Kompaktion zu quantifizieren. In einem Vergleich mit Ergebnissen aus pF- und ku- Untersuchungen von Sedimenten derselben Standorte durch GUENTHER (1991) sollte überprüft werden, welche Parameter des gestaltlichen Gefüges die Veränderungen der funktionalen Eigenschaften bestimmen. Der Vergleich fand beispielhaft an unkompaktierten und kompaktierten Bodenproben statt. ff

Description: The book is devoted to investigations of benthic fauna and geology of the Southern Atlantic Ocean. These works have been carried out in terms of exploring biological structure of the ocean and are of great importance for development of this fundamental problem. They are based on material collected during Cruise 43 of R/V Akademik Kurchatov in 1985-1986 and Cruise 43 of R/V Dmitry Mendeleev in 1989. Problems of quantitative distribution, group composition and trophic structure of benthos in the Southern Scotia Sea, along the east-west Transatlantic section along 31°30'S, and offshore Namibia in the area of the Benguela upwelling are under consideration in the book. Authors present new data on fauna of several groups of deep-sea bottom animals and their zoogeography. Much attention is paid to analysis of morphological structure of the Scotia Sea floor considered in terms of plate tectonics. Bottom sediments along the Transatlantic section and facial variation of sediments in the area of South Shetland Islands and of the continental margin of Namibia are under consideration.

Description: In der vorliegenden Arbeit werden Untersuchungen zur Verteilung des elektrischen Widerstandes in den südlichen zentralen Anden vorgestellt. Gestützt auf eine breite Datenbasis konnten mit Hilfe von ein- und überwiegend zweidimensionalen Modellierungen für Daten der Magnetotellurik und der Erdmagnetischen Tiefensondierung Modelle zur Verteilung des elektrischen Widerstandes in der andinen Kruste erstellt werden. Sie erlauben qualitative und quantitative Aussagen zur elektrischen Struktur in der Kruste. Im Andensegment von 21° bis 25° S wurden für einzelne Meßpunkte und für fünf mehrere 100 km lange Profile aus Nord-Chile, Süd-Bolivien und Nordwest-Argentinien Leitfähigkeitsmodelle erarbeitet. Elektromagnetische Untersuchnungen werden an einem aktiven Kontinentalrand durch den ’Küsteneffekt’ stark erschwert. Um den Küsteneffekt zu berücksichtigen, wurde der Pazifische Ozean bei einem zweidimensionalen Modell für ein Profil von der Küste bis in die Hochkordillere als ’Randbedingung’ mitmodelliert. Aus drei zweidimensional modellierten W-E-Profilen konnte ein alle morphostrukturellen Einheiten der Anden querendes Gesamtmodell auf der Breite von ca. 21°30’ S abgeleitet werden. Folgende Hauptmerkmale werden im Modell von W nach E beobachtet: • Unterhalb der Küstenkordillere ist der Widerstand mit größer als 3000 ihn relativ hoch. In diesem Bereich wird aber parallel zur Streichrichtung ein guter Leiter in der oberen Kruste gefunden, der lamelliert vorliegen muß. • Der Widerstand der ’normalen’ andinen Kruste ist bis in große Tiefen mit Werten von 50 bis 200 Ωm relativ gering. • Eine große Leitfähigkeitsanomalie liegt unterhalb der Westkordillere in geringer Tiefe. Sie erreicht eine integrierte Leitfähigkeit von ca. 25000 S. • Eine weitere Leitfähigkeitsanomalie mit einer integrierten Leitfähigkeit von ca. 14000 S wird unterhalb des Altiplano in der unteren Kruste beobachtet. Sie steigt von W nach E in die obere Kruste auf, und die integrierte Leitfähigkeit nimmt im westlichen Teil der Ostkordillere deutlich zu. Die Anomalie endet abrupt östlich von La Quiaca (ca. 65°30’ W). Im Ostteil der Ostkordillere wird ein relativ hoher Widerstand (ca. 500 Ωm) von der Oberfläche bis in große Tiefen beobachtet. • Das Vorland der Anden ist durch eine gut leitende Bedeckung charakterisiert. Der Widerstand der Lithosphäre nimmt von W nach E auf mehr als 3000 Ωm zu. Als Ursache der erhöhten elektrischen Leitfähigkeit werden für den guten Leiter unter der Küstenkordillere Kluftsysteme angesehen, in denen das in der subduzierten Platte vorhandene freie Wasser aufsteigt. Der extrem gute Leiter unter der Westkordillere kann im Einklang mit seismischen und gravimetrischen Untersuchungen als partiell geschmolzene Kruste interpretiert werden. Die Leitfähigkeitsanomalie unterhalb des Altiplano und der westlichen Ostkordillere könnte hingegen teilweise durch massive Vererzungen aber auch durch tektonische Ursachen begründet sein, wie z.B. tiefreichende Auf- und Abschiebungshorizonte, in denen Fluide vorhanden sind.

Description: The purpose of the present work is the research regarding the distribution of the electrical resistivity in the southern part of Central Andes. Supported by a considerable database and with the aid of one- and two-dimensional modelling tools developed for magnetotelurics and deep geomagnetical sounding, several models of the distribution of the electrical resistivity in the Andean crust were developed. They allow qualitative and quantitative insights related to the electrical structure within it. In the Andean segment between 21° and 25° S, several isolated measure stations and five regional profiles each of several 100 km length were processed to establish conductivity models for northern Chile, southern Bolivia and northwestern Argentina. Within this research work the ’coast effect’ at an active plate margin has to be taken into account and for this purpose, the Pacific Ocean was included as a boundary condition in a 2D model extending from the Pacific up to the High Andes. Based on three 2D modelled E-W oriented profiles, a greater model could be derived that involves all the present morphostructural units at a latitude of 21° 30’ S. These models showed mainly that: • below the Coastal Cordillera, the resistivity ranging within 3000 Ωm is comparatively high. Nevertheless, in this region a strike-parallel oriented conductor in the upper crust could be identified, which has to be lamellated. • down to great depths the resistivity of the ’normal’ Andean crust is relatively small, having values of 50 to 200 Ωm. • beneath the Western Cordillera, a shallow conductivity anomaly reaches total conductance of about 25000 S. • another conductivity anomaly with a total conductance of ca. 14000 S has been identified in the lower crust below the Altiplano. This anomaly reaches shallower levels to the east, and in the western part of the Eastern Cordillera, the total conductance increases. Eastwards of La Quiaca (ca. 65° 30’ W) the anomaly terminates abruptly. In the eastern part of the Eastern Cordillera a relatively high resistivity from the surface down to great depths was observed. • the Andean foreland shows a cover with good conductivity values. Beneath, the resistivity increases downward up to more than 3000 ßm from W to E. As a cause of the increased conductivity beneath the Coastal Cordillera, joint systems could account for the uprise of free water generated during the subduction of the Nazca plate. The extremely good conductor below the Western Cordillera can be interpreted together with gravity and seismic evidences as a partial melted crust. Besides, the conductivity anomaly beneath the Altiplano and the western Eastern Cordillera can be explained partly through the existence of ore deposits but also in terms of thrust tectonics, where the detachment zones are characterized by the presence of fluids.

Description: thesis

Description: DFG, SUB Göttingen

Description: Für die dreidimensionale Konstruktion und Visualisierung gestörter geologischer Schichtverbände wurde ein Systemverbund zur graphisch-interaktiven 3D-Flächenmodellierung auf der Basis geologischer Profildaten geschaffen. Die Verifizierung des Systems erfolgte anhand der Konstruktion eines 3D-Flächenmodells der Erftscholle (Niederrheinische Bucht). Zunächst wird die geologische Entwicklung und die heutige Situation des Untersuchungsgebietes beschrieben. Es werden auf die verwendete Datenbasis, bestehend aus Profilen, Bohrungen und Tiefenlinienpläne sowie die Interpretation, Aufarbeitung, Erfassung und Verwaltung der Daten eingegangen. Es schließt sich die Erläuterung des Systemverbundes an, der unter einer programmierbaren Anwenderoberfläche sowohl kommerzielle als auch freie Software vereinigt. Dieses anwendungsspezifisch gestaltbare System vereinigt Funktionen des Datenbankmanagements, der Visualisierung und der interaktiven 3D-Flächenkonstruktion auf CAD-Basis miteinander. Der offene modulare Aufbau des Systemverbundes ermöglicht die Anpassung an die spezifischen geologischen Anforderungen und die aktuellen Aufgabenstellungen. Dabei erlaubt die Interaktivität bei der Konstruktion und Visualisierung das Einbringen von Fachkenntnissen und Zusatzwissen in den Modellierungsprozess sowie eine gezielte Analyse komplexer 3D-Sachverhalte. Methodische Grundlagen der angewendeten Flächenkonstruktion auf der Basis irregulärer Dreiecksvermaschungen werden erläutert, und auf unterschiedliche Ansätze der Triangulierung eingegangen. Die Approximation natürlicher Flächen geschieht dabei durch ebene polygonale Facetten. Aufbauend auf diesen Grundlagen erfolgt die 3D-Flächenkonstruktion ausgewählter Schicht- und Störungsflächen aus dem Bereich der Erftscholle. Die einzelnen Arbeitsgänge von der Datenselektion über die Konstruktion bis zur Analyse des Flächenverbandes werden besprochen, um sowohl die gewählten Konstruktionsansätze, als auch die Funktionalität des Systemverbundes zu beschreiben.

Description: A soft and hardware system was combined for construction and visualisation of faulted geological strata units. Based on geological cross-sections, the system enables the graphical interactive 3D-surface modeling. By constructing the 3D-layermodel of the Erftblock (Lower Rhine Basin, Germany) the system was verified. First a description of the geological evolution and the present situation of the exploration area is provided. In addition the used data will be explained. This consists of cross-sections, wells, isopleth maps as well as the interpretation, processing, recording and management of the data. Then follows an illustration of the system. It joins commercial and free software under a programable user interface, which allows an optimisation of this tool depending on the necessary applications. The system unifies functions of database management, 3D-visualisation and interactive 3D-construction based on CAD-methods. The open and modular design of the system enables the adaption to specific geological requirements and current tasks. In particular, the interaction in terms of construction and visualisation allows the insertion of expert knowledge and additional facts into the modeling process. It also provides the possibility for exact analysis of complex 3D-objects. Methodical elements of the used construction process that are based on irregular triangulation will be explained. References to diferent approaches of triangulation will be revealed. In this work the approximation of natural surfaces is realized by means of flat and polygonal facets. This method form the base of the 3D-construction of the Erftblock, by which certain selected fault- and strata-boundaries are considered. To describe the function of the system and the approach for construction the singel steps of modeling will be pointed out. The process of modeling consists of data selection, construction, and finaly the analysis of the 3D-surface arrangement.

Description: thesis

Description: DFG, SUB Göttingen