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  • 1
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    An adaptive shallow water model on the sphere (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: This thesis describes the adaptive shallow water model PLASMA-FEMmE. It solves on the sphere the shallow water equations, the prototype for partial differential equations in atmospheric modeling, using a semi-implicit semi-Lagrangian time step and linear finite elements. Both statically and dynamically adapted grids created by the grid generator amatos are investigated. The results are compared with those of the predecessor model FEMmE that uses a static uniform grid. The outcome demonstrates the capability of the chosen approach as well as its limits. Grid adaptation can easily be achieved with amatos. No reflexions at the grid interfaces are observed. Though in one test case instabilities are released at the grid interfaces. The numerical errors are reduced without a considerable enhancement of the computational effort in another test case with a well-known analytical solution. In respect to the conservation properties the results are more complicated. Mass conservation can be achieved in one test case with an appropriate static grid. In case of complex flow regimes all conservation properties are weakened during the simulation using dynamic grid adaptation...
    Description: thesis
    Keywords: 532.5 ; 551.46 ; 550 ; Meteorologische Modelle ; Fluiddynamik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 135 S.
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  • 2
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    Evaluation and application of GPS and altimetry data over central Dronning Maud Land, Antarctica (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The polar ice sheets are unique paleoclimatic archives and play an important role in recent and future climate. The melting of the big freshwater reservoirs will not only increase the global sea level, but will also influence the ocean currents. Therefore, it will be of particular interest to improve the currently available numeric climate models to achieve more accurate statements about climatic change and its consequences. In this work, the evaluation and the different applications of GPS and altimetry data will be described in respect to enhance models. The antarctic area of investigation, Dronning Maud Land (DML), is of particular interest for German polar research, because both the overwintering station Neumayer and the summer station Kohnen are located within it. In the surroundings of these two stations, highly accurate kinematic GPS measurement were made, which will be the basis for the digital elevation model presented here. Because these data are spatially limited, they are supplemened with remotely sensed data. For this purpose, two airborne altimetry data sets and spaceborne laser altimetry data of the Ice, Cloud, and land Elevation Satellite (ICESat) are used...
    Description: thesis
    Keywords: 551.312 ; 551 ; 550 ; TWC 600 ; VAR 980 ; TQI 000 ; TSY 200 ; Geophysikalische Satellitenfernerkundung ; Antarktis {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 140 S.
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  • 3
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    Assessing the fidelity of the marine sedimentary magnetic record (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Marine sediments, diagenesis, anoxic environments, paleomagnetism, low-temperature magnetism, magnetic Fe-Ti-Oxides. - Magnetic particles usually occur in very minor concentrations in igneous and sedimentary rocks, soils, volcanic ashes, dusts and even in living organisms. Many of these magnetic grains are capable of carrying a stable permanent magnetization and therefore act as recorders of the recent and ancient Earth's magnetic field. Thus paleomagnetism refers to the study of this remanent magnetization in sedimentary and volcanic rocks through time. From this magnetization, directional intensity information can be recovered concerning the geomagnetic field that prevailed at the sample location at the time of the rock formation. The magnetic parameter on which such paleomagnetic studies are based is the natural remanent magnetization (NRM). In continental margin regions the remanence acquisition process is often complicated by post-depositional modifications of the original magnetic material. After deposition magnetic minerals can be altered or new magnetic phases can be formed. Consequently the original NRM might be obscured or even fully erased. The process of diagenesis and authigenesis may thus seriously compromise paleomagnetic interpretation. Therefore our knowledge of the geomagnetic field behavior based on sediment records from continental margin regions remains limited. To obtain fully reliable information about the geomagnetic field or paleoenvironmental conditions from continental margin regions, the effect of early diagenetic processes occurring after deposition of the sediment must be understood in detail.
    Description: thesis
    Keywords: 551.4686 ; 538.727 ; 550 ; TOT 320 ; VKB 380 ; TSZ 100 ; Paläomagnetismus {Geophysik} ; Sedimente bestimmter Regionen ; Atlantischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 113 S.
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  • 4
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    Seafloor seepage in the Black Sea (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Black Sea, seafloor seepage, mud volcanoes, seeps, fluid migration, gas hydrates, diapirs. - The Black Sea is the worldwide largest anoxic basin with thick gas rich sediments facilitating seafloor seepage, which is widely distributed along the continental slopes of the Black Sea. In two areas, the Sorokin Trough off Crimea and at the continental slope off Batumi (Georgia), the distribution, structure and evolution of two different vent systems and their relation to fluid migration pathways and gas/gas hydrate occurrences have been investigated by means of high resolution multichannel seismic data. In both regions, the distribution of seafloor seepage is controlled by fluid migration along permeable pathways associated with diapiric uplift in the subsurface. In the Sorokin Trough, seepage is expressed by intensive material upflow and the formation of mud volcanoes; offshore Batumi, gas seeps with low material flux dominate. In the Sorokin Trough, most mud volcanoes are associated with near-subsurface mud diapirs. The great morphological variability of the mud volcanoes reflects different driving mechanisms, which depend on the availability of permeable fluid migration pathways and the depositional environment. A 3D seismic dataset images the detailed three-dimensional ...
    Description: thesis
    Keywords: 551.466 ; 550 ; TSZ 100 ; VAT 300 ; VEZ 120 ; TQC 600 ; Atlantischer Ozean {Geophysik} ; Geologie des Meeresboden ; Randmeere {Geologie} ; Tiefseeseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 154 S.
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  • 5
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    Development of a novel balloon-borne optical sonde for the measurement of ozone and other stratospheric trace gases (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Ozone, balloon-borne measurements, atmospheric trace gases, concentration profiles, climate change. - In the frame of this work, a new small-size balloon-borne sonde was developed. A miniature grating spectrometer in the sonde measures simultaneously the solar spectral irradiance at a wide wavelength range from 200 to 850. As a first application, ozone profiles have been determined by measuring the changes in the spectral irradiance, caused by ozone absorption in the Huggins band. The wide spectral coverage of the spectrometer offers the possibility for measurements of other trace gases which absorb within the wavelength range, e.g. NO2 and BrO. The low weight of the new sonde (1.7 kg), the moderate price, and the autonomous portable telemetry system makes it a very versatile tool for satellite validation and for case studies, which requires a high number of launches. The newly developed sonde works well without temperature stabilisation, even so the spectrometer experiences rather large temperature changes (15 - 20 K) during the ascent through the atmosphere. Laboratory measurements were performed in ...
    Description: thesis
    Keywords: 551.5 ; 551.8 ; 550
    Language: English
    Type: monograph , publishedVersion
    Format: 148 S.
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  • 6
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    A new algorithm to retrieve the sea ice concentration using weather-corrected 85 GHz SSM/I measurements (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Sea ice is a very important component of the climate system. While the Arctic sea ice extent has retreated during the past 20 years, it has remained constant in the Antarctic. In order to better understand the role of sea ice in the climate system in the context of global warming currently used coupled Atmosphere-Ocean Global Circulation Models have to be improved. This requires to know the sea ice concentration C for a long period for both hemispheres and at the best possible spatial resolution. Currently used methods to obtain C like the NASA Team (NT) algorithm are based on data acquired by the Special Sensor Microwave/Imager (SSM/I) at 19 and 37GHz. The SEA LION (SL) algorithm presented here allows to infer C from the polarization P at 85GHz taking advantage of the higher spatial resolution at this frequency. However, the decrease of P caused by the weather influence leads to an overestimation of C. Therefore, P is corrected using a radiative transfer model and atmospheric data taken from Numerical Weather Prediction models and/or derived from SSM/I measurements. The various sea ice and snow properties are considered calculating monthly sea ice tie points. The average standard deviation of C derived with the SL algorithm is 12% for C 〈 50% and below 5% for C 〉 90%. The SL ice edge agrees within 10km with the one evident in VIS/IR images. The SL ice concentration gradient across the marginal ice zone (MIZ) agrees much better with the one evident in SAR images compared to results of the NT algorithm. Using the higher spatial resolution at 85GHz the SL algorithm allows to detect smaller open water areas than known algorithms. A major limitation of the SL algorithm arises from the quality of atmospheric data needed for the weather correction. A spatial resolution of these data lower than the 85GHz SSM/I channels and/or a time lag larger than half an hour between both data sets can cause relative errors above 100%, particulary in the cloud-covered parts of the MIZ.
    Description: thesis
    Keywords: 550.28 ; 551.31 ; 550 ; TWH 500 ; TWC 100 ; Einfluss von Eis {Klimatologie} ; Instr. Ergebn. zu Klimaänderungen und Klimaschwankungen
    Language: English
    Type: monograph , publishedVersion
    Format: 186 S.
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  • 7
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    Antarctic ice sheet expansions in the Middle Miocene and Pliocene (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: This study focuses on the interactions between climate and ice sheets in order to obtain a better understanding of the processes involved. Two periods in the geological past are explored; the Middle Miocene and the mid-Pliocene. For both periods, foraminiferal oxygen-isotope records from deep-sea sediment cores as well as stratigraphical data, suggest a global sea-level lowering. The magnitude of these reductions in sea level indicate large-scale ice-sheet build-up. However, the origin of these events and even the geographic locations of the ice sheets, are still under discussion. The ice sheet-climate model developed in this study provides a tool to test some of the hypotheses brought forward to explain the ice-sheet expansion events. It describes the Antarctic ice sheet and is forced by a climate component based on energy and mass balances. Further more, the model computes the oxygen-isotopic composition of the ice-sheet, thereby providing the possibility to compare numerical results directly to deep-sea sediment records. Numerical experiments focus on the interactions between atmospheric CO2, temperature, ice volume (sea-level equivalent) and the isotopic composition of sea water...
    Description: thesis
    Keywords: 551.69 ; 551 ; 550 ; TWC 600 ; VAR 980 ; Paläoklimatologie ; Antarktis {Glazialgeologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 137 S.
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  • 8
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    Palaeoenvironmental evolution of the Tunisian carbonate platform margin (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The Late BarremianLate Aptian interval was characterised by several major changes in the ocean/climate system related to the onset of the Mid-Cretaceous greenhouse world. North Africansedimentary deposits offer excellent archives of the ecological changes on the southern Tethyscontinental margin during this time interval. In the present phD thesis sedimentology, palaeontology,biostratigraphy, chemostratigraphy, and geochemistry are combined to reconstruct the palaeoenvironmental evolution and sea-level changes of the Tunisian carbonate platform margin.Respect is paid to major palaeoceanographic and palaeoclimatic events including the late Early Aptian Oceanic Anoxic Event 1a (OAE 1a) and two time intervals associated with widespread carbonate platform drowning in the early- and mid-Late Aptian. The last chapter deals with the cephalopod fauna of the platform margin. Results of the detailed regional investigations are compared to global marine palaeoenvironments and discussed in a broad geological context...
    Description: thesis
    Keywords: 551.77 ; 551 ; 550 ; TWC 600 ; VKB 372 ; VEN 130 ; VDH 300 ; Paläoklimatologie ; Karbonatische Sedimentgesteine ; Tunesien {Geologie} ; Kreide
    Language: English
    Type: monograph , publishedVersion
    Format: 160 S.
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  • 9
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    Atmospheric parameter retrieval from UV-vis-NIR limb scattering measurements (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The hyperspectral UV-vis-NIR spectrometer SCIAMACHY will be launched aboard the European satellite Envisat. Its limb measurements will provide vertically resolved profiles of trace gases and other atmospheric parameters. No retrieval algorithms and radiative transfer models have been established for these measurements yet.In this thesis, a unique, fast radiative transfer model for UV-vis-NIR limb radiances has been developed, implemented, and validated. It takes into account the sphericity of the atmosphere and up to two orders of scattering and surface reflection. The weighting functions for all parameters are calculated from analytical formulae. A realistic instrument model with field-of-view integration and signal-to-noise computation and retrieval algorithms have also been implemented. All have been combined in the new program package SCIARAYS. The package has been applied for the characterisation of the limb measurements in several ways:The simulated weighting functions agree well with those due to full multiple scattering. Thus they may be used to calculate theoretical precision estimates and averaging kernels. In conformance with this, test retrievals with approximate weighting functions converge correctly. Therefore, the approximate weighting functions of SCIARAYS are well suited for retrievals from SCIAMACHYś limb measurements.Detailed theoretical retrieval precisions have been calculated for SCIAMACHYś trace gas targets. The conclusion is that a UV-vis-NIR limb sensor like SCIAMACHY is well suited for studying the vertical structure of the stratosphere and also of the upper troposphere above cloud top.Further investigations show that the vertical resolution of retrievals from SCIAMACHYś limb measurements can be improved beyond its geometrical limits. As a trade-off for better vertical resolution, the retrieval precision gets worse. Thus O3 profile features with 1km vertical extent will be detectable with a precision of 20-30%.
    Description: thesis
    Keywords: 551.5 ; 550.28 ; 550 ; TUA 850 ; TQI 000 ; TVA 210 ; Satellitenmeteorologie ; Geophysikalische Satellitenfernerkundung ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 247 S.
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  • 10
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    Near-surface sediment structures at cold seeps and their physical control on seepage (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The major objective of the study is to investigate how near-surface sediment structures and other geological aspects control the nature and occurrence of cold fluid seepage. Mainly high resolution multichannel seismic data and swatch bathymetry data were used to study nearsurface seismostratigraphy, structure and seismic fluid-indicating features in two different fluid seepage provinces: Campeche Knolls, southern Gulf of Mexico and the frontal Makran, offshore Pakistan. The two areas have fundamentally different tectonic settings: The Campeche Knolls, southern Gulf of Mexico represents a passive margin influenced by salt tectonism, while the frontal Makran is the most basinward part of the Makran accretionary prism, characterized by plate subduction, sediment accretion, thrust faulting and development of sediment imbricate slices. However, they share quite a few similarities in shallow sediment structures and fluid seepage patterns...
    Description: thesis
    Keywords: 551.23 ; 553.28 ; 550 ; TSZ 100 ; VAE 880 ; TSZ 200 ; Atlantischer Ozean {Geophysik} ; Passive und aktive Kontinentalränder {Geologie} ; Indischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 125 S.
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  • 11
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    Modeling of radiative transfer through a spherical planetary atmosphere (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: During the last years and decades issues related to the physics and chemistry of the Earthś atmosphere have attracted much scientific and public interest. The most important problems are stratospheric ozone loss and the ò̀zone hole ́́above Antarctica, global warming and climate change, and tropospheric air pollution. The understanding of the impact of human activities on the Earthś atmosphere requires measurements on a global scale. These enable the spatial and temporal variability of the atmospheric constituents to be investigated. Recently efforts have been made to establish a global observation system comprising satellite instruments and ground-based networks. To process data supplied by the instruments which belong to the global observation system, the development of radiative transfer models and retrieval algorithms is essential. This thesis contributes to the development of the radiative transfer models and retrieval algorithms intended to interprete measurements of the spectral radiance scattered in the atmosphere or transmitted through the atmosphere in UV-Vis-NIR spectral region performed by a new-generation remote sensing satellite spectrometer SCIAMACHY. In this study, main problems of radiative transfer through a spherical planetary atmosphere compared to a plane-parallel atmosphere are investigated. An efficient spherical radiative transfer model intended to simulate SCIAMACHY limb measurements was developed and validated. The model can also be used for the interpretation of measurements performed by other space-borne instruments as well as to compute air mass factors for ground-based measurements. An approximate approach allowing the simulation of limb measurements to be substantially accelerated was developed and its accuracy was investigated. Furthermore, a numerical radiative transfer model intended to simulate SCIAMACHY occultation measurements was developed and then coupled with an appropriate selected inverse technique.
    Description: thesis
    Keywords: 551.5 ; 550.28 ; 550 ; TQI 000 ; Geophysikalische Satellitenfernerkundung
    Language: English
    Type: monograph , publishedVersion
    Format: 150 S.
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  • 12
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    Tectonic and magmatic processes along the transform margin of Southern Africa (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Giant shear processes shaped Africa's southern margin during the breakup of the supercontinent Gondwana. They acted along a more than 1000 km long transform fault, whose remnant structure the Agulhas-Falkland Fracture Zone stretches today from the Falkland Plateau to the southeastern margin of Africa. A study of the processes which initiated such a long-offset transform fault and acted during their active phase is essential to understand how this sheared margin developed. Africa’s southern margin is not only one of the best examples to study the sharp continent-ocean-transition zones, the marginal ridge, fracture zone, and basin structures usually associated with transform margins, but it provides the unique opportunity to study how excessive magmatic processes acted which formed a Large Igneous Province at a sheared margin. In this thesis, I use seismic refraction, seismic reflection data and plate-tectonic reconstructions to investigate the structure and dynamics of this margin. These are ideal methods as they lead to high-quality velocity-depth models showing the present-day structure across the margin and provide timing and geometries by means of plate kinematics...
    Description: thesis
    Keywords: 550 ; TSR 000 ; TSZ 200 ; VAE 880 ; VAE 890 ; VER 100 ; VEZ 200 ; Südafrika {Geophysik} ; Indischer Ozean {Geophysik} ; Passive und aktive Kontinentalränder {Geologie} ; Ozeanische Kruste {Tektonik} ; Republik Südafrika {Geologie} ; Indischer Ozean {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 157 S.
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  • 13
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    Airborne-based geophysical investigation in Dronning Maud Land, Antarctica (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Antarctica represents a key component in the investigation of the geological history and reconstruction of the supercontinents Rodinia and Gondwana. Remnants of the formation and disintegration of these former land masses can be found, although great uncertainties remain in the location of tectonic boundaries beneath the ice sheet of Antarctica due to general lack of outcrops and the limited amount of geological data. Space and airborne measurements are the only possibility to obtain comprehensive spatial data coverage of geophysical data over the extensive large polar areas. Common knowledge of the geological framework displays three major tectonic events which formed Dronning Maud Land (DML): the Grenvillian Orogen (1.1 Ga) build up Rodinia, the Pan-African-Antarctic Orogen (EAAO, 500 Ma) rose in the supercontinent Gondwana and finally the breakup of Gondwanaland, at around 180 Ma...
    Description: thesis
    Keywords: 526.7 ; 559 ; 538.87 ; 550 ; TSY 200 ; Antarktis {Geophysik} ; Aerogeophysik
    Language: English
    Type: monograph , publishedVersion
    Format: 174 S.
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  • 14
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    Imaging of Cenozoic climatic events and bottom water activities at the northeastern flank of Walvis Ridge: A correlation of seismic data with borehole data measurements (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Seismic, marine, walvis ridge, bottom currents, climatic events. - The history of sedimentation and current activities at the northeastern flank of Walvis Ridge is investigated by a correlation of multichannel seismic data collected during R/V Meteor Cruise M49/1 in early 2001 with borehole measurements of Ocean Drilling Project (ODP) Leg 208. During Meteor Cruise M 49/1 multi-frequency seismic data were collected using two different seismic sources, in a quasi simultaneous mode in order to get best possible penetration and resolution of the sub-surface structures. Walvis Ridge divides the southeastern Atlantic Ocean into two basins, the Angola Basin to the north and the Cape Basin to the south. It is well known as an impassable barrier for bottom waters which separates Antarctic Bottom Waters (AABW) widely distributed in the Cape Basin from North Atlantic Depth Waters (NADW) in the Angola Basin. The sediments of the northeastern flank of Walvis Ridge are characterized by mostly undisturbed sequences of Cenozoic sediments, with varying thickness of ~150 m at the edge of the Angola Basin and ~450 m at the axis of the ridge. A correlation of seismic data with borehole data was accomplished by calculating synthetic seismograms using GRA density measurements of the cores and an averaged velocity model. This 'simple' event modeling allows to assign ages to the seismic reflectors and to identify key horizons/boundaries like the E/O and the K/T boundaries as well as the ELMO event and deposits of the PETM, representing Cenozoic climatic events. The seismic pattern of these target horizons shows similar properties at the different sites indicating their regional distribution. A special static correction in addition to standard seismic processing steps resulted in high quality high resolution deep sea Watergun images. A comparison between the seismic images and the magnetic core ...
    Description: thesis
    Keywords: 551.69 ; 551.462 ; 551 ; 550 ; Tiefseeseismik {Geophysik} ; Atlantischer Ozean {Geophysik} ; Geologische Bohrungen in einzelnen Regionen ; Teilgebiete {Atlantischer Ozean: Geologie} ; Marine Sedimente einzelner Meere und Ozeane {Geologie} ; Paläoklimatologie
    Language: English
    Type: monograph , publishedVersion
    Format: 133 S.
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  • 15
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    The Phanerozoic thermo-tectonic evolution of northern Mozambique constrained by 40Ar/39Ar, fission track and (U-Th)/He analyses (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Thermochronology, Fission track, (U-Th)/He, 40Ar/39Ar,Mozambique, Gondwana, supercontinent dispersal. - Results of thermochronometric investigations comprising 40Ar/39Ar hornblende and biotite, titanite and apatite fission track (FT) and apatite (U-Th)/He dating on 102 basement rock samples from northern Mozambique record a cooling and denudation history since Early Palaeozoic times. In the north Mozambican sector, these results place new temporal and geometric constraints on the initial rift and subsequent drift configuration during the Gondwana supercontinent dispersal as well as on the post break-up evolution of the sheared margin of central East Africa. Furthermore, they highlight the influence exerted by ductile basement structures of Pan-African age on the loci of tectonically active zone and associated denudation since the Late Palaeozoic. 40Ar/39Ar hornblende and biotite ages range from c. 542 Ma to 456 Ma and c. 448 Ma to 428 Ma, respectively. They record the cooling from the latest Pan-African metamorphic imprint, presumably related to the formation of the Namama Thrust Belt at c. 550-500 Ma, at slow rates of about 11Âʿ 7ÂʿC/Ma from 525ÂʿC to 305ÂʿC in Early to Late Ordovician times. Locally, the thermal influences of syn- to post-tectonic granitoid / pegmatite emplacements at about 500-450 Ma delayed cooling. Widespread basement cooling to 〈 350ãA°C occurred in Late Ordovician to Early Silurian times. The titanite fission track ages fall into two age groups of c. 378 Ma to 327 Ma and c. 284 Ma to 219 Ma. Very slow cooling since the Late Ordovician/Early Silurian at rates of 〈 1ãA°C/Ma to below 275 ãA« 25ãA°C in the Late Devonian/Early Carboniferous is deduced from the older titanite FT ages. It is related to decreasing denudation in ...
    Description: thesis
    Keywords: 551.701 ; 556 ; 551 ; 550 ; VBN 500 ; Geochronologie einzelner Regionen im allgemeinen
    Language: English
    Type: monograph , publishedVersion
    Format: 265 S.
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  • 16
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    Diagenetic imprints on magnetic mineral assemblages in marine sediments (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Diagenesis, Rock magnetism, Marine sediments. - Sediments and sedimentary rocks are important sources for paleomagnetic studies of the geomagnetic field behaviour and of environmental changes. These studies are greatly dependent on the reliable extraction of the detrital magnetic signal. Overprinting of this signal by reductive diagenetic processes, where iron-bearing minerals are dissolved and secondary (magnetic) sulphide minerals form, jeopardizes the validity of such investigations. It is therefore necessary to be aware of the possible presence of diagenetic/authigenic magnetic phases, i.e. greigite, and their influence on the paleomagnetic signal. A chemical remanent magnetisation (CRM) due to these phases can obscure the detrital magnetic signal. It remains to be shown how primary detrital minerals may survive dissolution under these conditions, and by which mechanisms secondary (magnetic) sulphide minerals are formed.
    Description: thesis
    Keywords: 538.7 ; 552.5 ; 550 ; TOT 310 ; VKB 323 ; TOT 310 ; VKB 323 ; Gesteinsmagnetismus {Geophysik} ; Sedimentphysik
    Language: English
    Type: monograph , publishedVersion
    Format: 118 S.
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  • 17
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    Reconstruction of the Phanerozoic tectono-thermal history of central and southern Madagascar, based on fission track thermochronology (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Madagascar, Gondwana, thermochronology. - Titanite and apatite fission track (FT) thermochronology on 127 basement and 18 sedimentary rock samples from central and southern Madagascar record a complex cooling and denudation history since the Early Palaeozoic. Titanite FT analyses gave ages ranging between 483 Ma and 266 Ma. Apatite FT ages vary between 460 Ma and 79 Ma. Samples from Late Carboniferous to Jurassic sediments from the Morondava basin gave apatite FT ages ranging between 462 Ma and 184 Ma. FT data argues for reactivation of several Late Neoproterozoic/Early Cambrian ductile shear zones pre-dating the initial opening of the Morondava basin during the Late Carboniferous. Apatite FT data indicate that the subsequent Mesozoic rift evolution was accompanied with an eastward migration of areas of fast cooling. During Mesozoic times the Morondava basin had a greater eastward extension. Detrital apatite FT data derived from the outcropping Sakoa Group imply that after the Late Carboniferous deposition these rocks were covered by 2-4 km of sedimentary rocks. The final separation of Madagascar and East Africa during the Jurassic influenced mainly samples in southwest Madagascar, where basement regions and also former basin regions were exhumed. Combined Titanite FT and structural data argue for a minor tectono-thermal influence of the Marion hot spot during the Madagascar-India separation. However, apatite FT ages and modelled cooling paths indicate that the break-up during the Cretaceous was associated with a denudation amount of ~4 km crustal section along a narrow stripe parallel to the present eastern continental margin.
    Description: thesis
    Keywords: 551,701 ; 550 ; VBN 500 ; VBN 200 ; VEQ 300 ; VBN 500 ; VBN 200 ; VEQ 300 ; Geochronologie einzelner Regionen im allgemeinen ; Radiometrische Altersbestimmung ; Madagaskar {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
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  • 18
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    Sediment accumulation and diagenesis in the late quaterary equatorial Atlantic Ocean (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Nonsteady-state Diagenesis, Equatorial Atlantic, Rock-magnetic and Geochemical Multiproxy Approach, XRF Core Scanner, Fe Redox, Magnetite Dissolution. - This thesis investigates 25 Late Quaternary sediment records from the central Equatorial Atlantic by rock magnetic, geochemical and stratigraphical methods. The work was performed in the framework of the Collaborative Research Center 261 ‘The South Atlantic in the Late Quaternary: Reconstruction of Material Budgets and Current Systems’ funded by the Deutsche Forschungsgemeinschaft. The main objective was to analyze and distinguish terrigenous and diagenetic proxysignatures, in particular of rock magnetic parameters. All cores were correlated and dated on basis of their carbonate, iron and rock magnetic records. Magnetite coarsening and partial depletion was observed in glacial organic-rich layers, most intensely during oxygen isotope stages 6, 10 and 12. Non-magnetic and magnetic iron mineral enrichments were found below and at former and active Fe(II) / Fe(III) redox boundaries. Various new proxies quantifying magnetite reduction (ratio of Fe to magnetic susceptibility, ratio of non-ferrimagnetic to total magnetic susceptibility) and authigenesis (ratio of Fe to magnetic susceptibility) were established and found to be highly sensitive indicators of past redox conditions. Comparing these signals with the organic carbon records, it was shown, that rock magnetic, carbon and carbonate records in most parts ...
    Description: thesis
    Keywords: 551.9 ; 538.7 ; 551.46 ; 551 ; 550 ; TOT 320 ; TSZ 100 ; VKB 380 ; VDI 200 ; VEZ 100 ; VAT 240 ; Paläomagnetismus {Geophysik} ; Atlantischer Ozean {Geophysik} ; Sedimente bestimmter Regionen ; Quartär ; Atlantischer Ozean {Geologie} ; Marine Sedimente einzelner Meere und Ozeane {Geologie}
    Language: English
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  • 19
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    Reconstruction of the sedimentary history offshore NW Africa (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Paleoceanography, Climate, Marine Productivity, Terrigenous Input, High-frequent Cyclicities, LGM, Holocene, XRF Core Scanner. - The goal of this thesis is to reconstruct, with high spatial resolution, the influence of coastal upwelling and terrigeneous input on the magnitude and composition of sediment accumulation off NW Africa, and to investigate how this influence has varied through the last glacial and interglacial periods. To achieve dense coverage for paleoceanographic reconstruction in the investigation area, a large number of sediment cores has been analyzed with rapid and non-destructive core-logging systems. The results of this thesis show that even the small region of the Canary Islands can be separated into several areas, with each reflecting its own sediment characteristics. Recent remote sensing images of chlorophyll concentration reflecting the present upwelling conditions are mirrored by the accumulation rates of the underlying sediment. The variation and distribution of the sediment accumulation rates in the past provides information about paleoceanographic features, such as upwelling conditions and sea-level fluctuations. The contribution of terrigeneous material to the marine sediments can be separated into eolian and a fluvial portions. Three characteristic areas ...
    Description: thesis
    Keywords: 551.46 ; 550.28 ; 550 ; VAT 240 ; TSZ 100 ; VAT 240 ; TSZ 100 ; Marine Sedimente einzelner Meere und Ozeane {Geologie} ; Atlantischer Ozean {Geophysik}
    Language: English
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  • 20
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    Ozone depletion, chlorine activation and water vapor observed in Spitsbergen (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.5 ; 550 ; TYY 100 ; TVA 210 ; Arktis {Meteorologie und Klimatologie} ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
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