ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Laser ablation ICP-MS in paleoceanography (2010)
    Univ. Bremen
    Details
    Publication Date: 2017-06-09
    Description: The different benthic foraminiferal species (epibenthic as well as endobenthic) colonize wide areas of the ocean floor and are widely used for paleoceanographic reconstructions. To improve these reconstructions, it is an important part in research to continuously develop and refine proxies by e.g. improving measuring techniques as well as introducing other species in paleoceanograhpy. The main focus of the presented thesis is a regional examination of the trace element ratios of the rarely used benthic foraminifer Oridorsalis umbonatus and the investigation of their suitability for paleoceanographic applications. Since O. umbonatus is not very abundant in the sediments, it was necessary . as a prerequisite for such studies . to investigate, whether laser ablation ICP-MS can be used for trace element measurements on benthic foraminifera. Therefore, as a first step, trace elements were measured using laser ablation ICP-MS on a set of modern core top samples collected along a depth transect on the continental slope off Namibia at 25.5.S (320 . 2300m water depth; 2.9. to 10.4.C). The Mg/Ca ratios where than calibrated against bottom water temperatures (BWT). The study demonstrates clearly that benthic foraminiferal trace elements can be reliably measured with the laser ablation technique and that the Mg/Ca ratio of O. umbonatus has the potential to be used as a proxy for BWTs...
    Description: thesis
    Keywords: 579.44 ; 579.44 ; UHG 000 ; VXE 000 ; UHG 000 ; VXE 000 ; Paläoozeanologie ; Protozoa {Paläozoologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 81 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 2
    facet.materialart.
    Unknown
    The effect of acidic polysaccharides on the biogeochemistry of iron in the marine environment (2010)
    Univ. Bremen
    Details
    Publication Date: 2017-06-09
    Description: In the early 1990`s the first IPCC report stated the effect of anthropogenic CO2 emissions on global warming and John Martin`s Iron Hypothesis (Martin and J.H 1990), relating atmospheric dust deposition, a major source of iron to the surface ocean, to the CO2 concentration in the atmosphere and the last ice age, culminating in the well known sentence Give me (half) a tanker of iron and I’ll give you a new ice age!. Since then, several large-scale in situ Fe fertilisation experiments revealed that in large areas of the ocean, the so called high nutrient low chlorophyll (HNLC) areas, phytoplankton growth is partly limited by depleted Fe conditions (Geider et al. 1994; De Baar and Boyed 2000; Boyd et al. 2007). The ocean receives Fe from upwelling, riverine input, melting icebergs, atmospheric dust input, input from anoxic sediments, hydrothermal vents and direct recycling by organisms(Tovar-Sanchez et al. 2007). However, in HNLC regions the Fe input to surface waters is very low resulting in Fe limitation of phytoplankton growth. Fe is an important nutrient for marine phytoplankton (Geider et al. 1994; Falkowski et al. 1998; Morel and Price 2003), being essential in metabolic reactions like the photosynthetic electron transport and the assimilation of nitrogen. It is also required for the synthesis of chlorophyll (Martin et al. 1988; Maldonado et al. 1999) as well as for the functioning of the enzyme superoxide dismutase which inhibits the breakdown of chlorophyll by superoxide radicals (Coale 1991)...
    Description: thesis
    Keywords: 577.14 ; VJE 000 ; VJC 210 ; VJE 000 ; VJC 210 ; Organische Geochemie ; Geochemie des Meerwassers
    Language: English
    Type: monograph , publishedVersion
    Format: 106 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 3
    facet.materialart.
    Unknown
    Mg-Ca, B-Ca and U-Ca in shells of benthic foraminifers (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Mg/Ca ratios in benthic foraminiferal shells are frequently used in paleoceanographic studies to estimate past bottom water temperatures. Apart from temperature, other factors may exert additional influences on foraminiferal Mg/Ca. These include the Mg/Ca ratio of seawater, partial dissolution of shell calcite, salinity, physiological effects, and, probably of capital importance, the carbonate chemistry of seawater. In this context, the seperate effects of temperature and seawater carbonate chemistry on the magnesium incorporation into benthic foraminideral calcite are unraveled and quantified in this thesis...
    Description: thesis
    Keywords: 579.44 ; 579.44 ; 560 ; VXE 000 ; VJE 220 ; VXE 000 ; VJE 220 ; Protozoa {Paläozoologie} ; Geochemie der Fauna
    Language: English
    Type: monograph , publishedVersion
    Format: 88 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 4
    facet.materialart.
    Unknown
    Quantitative estimation of aerobic diagenetic overprint of palaeoproductivity signals (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Organic-walled dinoflagellate cysts, oxidation, degradation, organic matter. - Species-selective aerobic decomposition affects fossil organic-walled dinoflagellate cyst (dinocyst) records and hence dinocyst-based interpretations of primary productivity and oceanographic conditions. However, since the recognition of dinocyst species sensitive and resistant to oxic degradation (S- and R-cysts, respectively) it has become apparent that R-cysts may still serve as reliable productivity and oceanographic conditions proxies. On the other hand S-cysts provide a way to quantify aerobic degradation of organic matter (OM) and past bottom-water O2 concentrations. OM degradation plays a key role in global carbon cycling and is important for global climate change. Therefore dinocysts are a valuable tool for estimating the rate of diagenetic process. Questions concerning species-selective aerobic degradation still remain and will be adressed here. To obtain information on the rate of S-cyst decomposition, the relationship between S-cyst degradation and O2 concentrations, and the aerobic degradation of extinct dinocyst species, a natural exposure experiment has been conducted and studies of both Quaternary and pre-Quaternary material from sediment cores were executed. The exposure experiment was conducted in the natural setting of the Eastern Mediterranean. During a 15 month exposure period to oxic water masses, concentrations of S-cysts (Brigantedinium spp. and Echinidinium granulatum) decreased by 24 to 57%. However, taxa such as Nematosphaeropsis labyrinthus, Echinidinium aculeatum, Operculodinium israelianum and Impagidinium aculeatum demonstrated a slight increase in concentration, indicating resistance to aerobic degradation. These results show that even short-term exposure to oxygen may cause considerable changes in the dinocyst assemblage ...
    Description: thesis
    Keywords: 560 ; VVA 560 ; VXE 000 ; VVA 560 ; VXE 000 ; Aktuopaläontologie ; Protozoa {Paläozoologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 159 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 5
    facet.materialart.
    Unknown
    Distribution and transportation pathways of marine particulate matter off Northwest Africa (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Marine snow, underwater cameras, particle flux, aggregation, suspended particulate matter, particle transport. - This study focusses on the vertical distribution and transportation pathways of marine particles off NW-Africa with aid of optical methodologies. A profiling camera system and a remotely operated vehicle (ROV) was used for in-situ observations on the distribution, transport processes and sinking behaviour of marine particulate matter. Between the regional areas of investigation Cape Blanc, Dakhla and Cape Bojador significant differences could be observed with respect to distribution and transportation patterns. These differences are primarily related to the different primary production conditions between the investigation areas. Primary production is the most important factor for the abundance of particulate matter, where highest particle concentrations in the entire water column were seen off Cape Blanc. Next to primary production, water depth, currents and density gradients are factors influencing the particle distribution patterns. With respect to the prevailing transport processes, the Cape Blanc region is characterised by vertically orientated transport patterns. In addition to the continuous supply of large, relatively fast sinking particle aggregates a sinking event could be documented for the first time in-situ in the water column. These events deliver huge amounts of particulate matter from the ocean surface ...
    Description: thesis
    Keywords: 551
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 6
    facet.materialart.
    Unknown
    Sedimentary and stratal patterns in jurassic successions of western Madagascar (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Madagascar; Jurassic; Karoo; Gondwana; Breakup; Rift; Microfauna; Macrofauna; Ammonites; Indian Ocean. - The breakup of Gondwana along the former East African Orogen is widely interpreted to have lasted from the Late Palaeozoic to the Callovian. The present study indicates that the Permian-Triassic or Karoo phase of rifting was not responsible for the separation of East- and West-Gondwana, since that rift system failed in the Late Triassic. Instead the breakup of Gondwana occurred in the Late Liassic. The pre-rift phase in the Morondava Basin is represented by the Karoo deposits, and the syn-rift phase is recorded by Toarcian marine shales, locally overlain by Aalenian sandstones. A major Early Bajocian unconformity is interpreted as the breakup unconformity. The initial post-rift or drift phase is represented by the Bajocian-Bathonian carbonates, marls and sandstones of coastal plain environment and a coastal barrier/lagoon complex. During the Bathonian the siliciclastic shoreface system moved basinward. Callovian-Early Kimmeridgian shales with interbedded iron-oolites represent ...
    Description: thesis
    Keywords: 551 ; VAE 500 ; VDB 100 ; VEQ 300 ; Geotektonische Entwicklung der Erdkruste {Geologie} ; Gondwana ; Madagaskar {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 7
    facet.materialart.
    Unknown
    Biogeochemie gelöster Kohlenhydrate in der Arktis (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.9 ; VJE 200 ; VJC 210 ; Geochemie Lebender Materie ; Geochemie des Meerwassers
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 8
    facet.materialart.
    Unknown
    Production and preservation of calcareous dinoflagellate cysts in the modern Arabian Sea (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 560 ; VYF 200 ; Pyrrophyceae {Paläobotanik}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 9
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 10
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 11
    facet.materialart.
    Unknown
    Assessing the fidelity of the marine sedimentary magnetic record (2010)
    Univ. Bremen
    Details
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 12
    facet.materialart.
    Unknown
    Methane oxidation and carbon assimilation in marine sediments (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Anaerobe Oxidation of Methane, AOM, methanotrophy, stable isotope labeling, stable isotope probing, carbon assimilation, flow-through columns, ANME, Seep-SRB, Gullfaks, Tommeliten. - Anaerobic oxidation of methane (AOM) performed by consortia of methanotrophic archaea (ANME) and sulfate reducing bacteria (SRB) is the major sink of methane in marine sediments. This thesis describes methane consumption at two of the most active North Sea cold seeps (Gullfaks, Tommeliten), their microbial community and the resulting lipid biomarker patterns. Experiments in flow-through setups are presented, focusing on physiological parameters of AOM activity such as different methane and sulfate concentrations and on the tolerance of AOM to starvation periods. The roles of inorganic carbon (DIC) and methane as carbon sources for the microbial community performing AOM were examined combining stable isotope probing and lipid biomarker analyses. For archaea substantial uptake of carbon from DIC and methane was found, indicting a novel carbon assimilation pathway. Biomass from SRB was exclusively labeled by DIC indicating a methane dependent, but autotrophic growth consortial SRB.
    Description: thesis
    Keywords: 551.9
    Language: English
    Type: monograph , publishedVersion
    Format: 153 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 13
    facet.materialart.
    Unknown
    Seafloor seepage in the Black Sea (2010)
    Univ. Bremen
    Details
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 14
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 15
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 16
    facet.materialart.
    Unknown
    Remote sensing of the Northwest African upwelling and its production dynamics (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Carbon export; SeaWiFS; variability; upwelling; Atlantic Ocean; chlorophyll filament; SeaWiFS; SST. - The North Atlantic off NW Africa is characterized by the trade wind induced upwelling of cold and nutrient rich waters. As one of most strongest eastern boundary upwelling areas it is marked by low sea surface temperature and high bio-production, both subject to strong seasonal and interannual variations.Satellite measurements of sea surface temperature (SST) and chlorophyll-a (Chl-a) in the upper water-column were used to (a) recognize the upwelling of deep water and its distribution and mixing in the surface, (b) identify the development of phytoplankton blooms and (c) provide further insights in the characteristics of its variations.Measurements of surface Chl-a were compared to deep-sea fluxes of organic carbon in order to determine the relationship between both parameters and to further calculate the export of Corg and the export variation strength.The off-shore extension of SST-defined upwelling from 1988 through 1999 between 18ʿ and 25ʿN shows maxima in January and May/June with an average area of 140,000 km2 (standard deviation of 20,000 km2). Minima in August exhibit an extension of 43,000 km2 (15,000 km2 standard deviation). A correlation between ...
    Description: thesis
    Keywords: 910 ; UKB 100 ; Nordatlantik {Regionale Ozeanologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 17
    facet.materialart.
    Unknown
    Antarctic ice sheet expansions in the Middle Miocene and Pliocene (2010)
    Univ. Bremen
    Details
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 18
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 19
    facet.materialart.
    Unknown
    Enhanced analysis of stratified climate archives through upgrade of Laser Ablation Inductively Coupled Plasma Quadrupole to Time of Flight Mass Spectrometry? (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: ICP-MS, Time of Flight, laser ablation, solid and liquid samples, ice cores, Antarctica, mineral dust, trace element analysis. - The analysis of the inorganic composition of climatic archives provides proxies for climate reconstruction. For many applications commercially available inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS) systems are used for investigations. One aim of this thesis was to test the laser ablation (LA)-ICP-Q-MS method for the analysis of different sample matrices (polar ice cores, bivalves, frozen lake sediment cores). The main limitation of LA-ICP-Q-MS measurements is the number of analysed isotopes, especially for point scan analysis of embedded particles in the ice matrix and the analysis of growth bands of bivalve shells. Analysing as many isotopes as possible is of interest to deduce e.g. the corresponding source region of embedded particles in the ice matrix. The quasi-simultaneous detection of several isotopes of transient signals is realised in ICP-Time of Flight-MS (ICP-TOF-MS) systems. The applicability of the newly developed ICP-TOF-MS system for ice core analysis in climatic research was explored in this thesis. With the present experimental setup the analysis of trace elements in ice core samples is only possible for liquid samples. The accuracy and precision compares to well established ICP-Q-MS systems. Using the Aridus II as sample introduction system the signal sensitivity was 2-10 times lower for the ICP-TOF-MS compared to ICP-Q-MS systems. Calibration studies and investigation of reference materials showed that the calibration range is limited to an order of magnitude of about 10exp4 to 10exp5 except for m/z ratios between 23 amu and 72 amu where it is even lower. The observed ...
    Description: thesis
    Keywords: 551.6 ; VJA 240 ; TWC 100 ; TWC 500 ; VAR 980 ; Spektroskopische Verfahren {Geochemie} ; Instr. Ergebn. zu Klimaänderungen und Klimaschwankungen ; Klimaschwankungen und Klimaänderungen im Quartär ; Antarktis {Glazialgeologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 185 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 20
    facet.materialart.
    Unknown
    Sediment dynamics of megaslides along the Svalbard continental margin and the relation to paleoenvironmental changes and climate history (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Slope stability, submarine slides, Svalbard, Arctic Ocean, Sophia Basin. - With increasing interest in slope stability issues on continental shelves the causes and trigger mechanism of submarine slides get more and more into the scientific focus. Within the ESF EUROMARGINS project 'Slope Stabilities on Europe's passive continental Margin' (SPACOMA) sediment dynamics of megaslides along the passive continental margin north of Svalbard have been investigated. The study concentrated on identification and sedimentological characterisation of megafailure events, their dating and interpretation in relation to paleoceanography and climate history of the Svalbard archipelago. Integrated interpretation of multibeam bathymetric, sediment-penetrating acoustic (PARASOUND) and seismic data shows a multiple slope failure on the northern European continental margin, north of Spitsbergen. One huge submarine slide has been identified which was first described by Cherkis et al. (1999) - the Yermak Slide (later named Hinlopen/Yermak Megaslide). The extent of the Hinlopen/Yermak Megaslide has been revised based on new acoustic and detailed bathymetric data. Details from the side's internal structure give evidence for one main slide event followed by repeated minor events. The first slide event occurred during MIS 3 around 30 cal. kyr. BP and was characterised by highly dynamic and rapid evacuation of ca. 1.250 kmÃÂđ of sediment from the lower to the upper part of the shelf slope. During this megaslide event, headwalls up to 1600 m have been created and ca. 1150 kmÃÂđ material from hemipelagic sediments and from the lower preexisting trough mouth fan has been entrained and transported into the semi-enclosed Sophia Basin. This megaslide was followed by a secondary evacuation of debris material to the Nansen Basin accomplished by funnelling of the debris through the Littke Channel between Polarstern Seamount and the adjacent continental slope. The main slide debris is overlain by a set of fining-upwards sequences as evidence for the associated suspension cloud and ...
    Description: thesis
    Keywords: 551.307 ; 551.69 ; 551 ; Nordatlantische Polarinseln {Geologie} ; Sedimente bestimmter Regionen ; Sonstige Sedimentationsprozesse ; Paläoklimatologie
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 21
    facet.materialart.
    Unknown
    Retrieval of surface emissivity of sea ice and temperature profiles over sea ice from passive microwave radiometers (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Sea ice, surface emissivity, emitting layer temperature, temperature profile, microwave radiometry. - Polar regions play a key role in the global climate. The information on atmospheric parameters in these regions is sparse. Among the polar surfaces, sea ice varies in extent and physical properties with region and season and so does the surface emissivity. In the present study a method to retrieve the emissivity is applied over two selected regions in the Arctic, one covered by first-year ice and the other by multiyear ice and it investigates the application of them in the improvement of temperature profile retrieval ver sea ice. The retrieval of surface emissivity is done by combining simulated brightness temperatures with the satellite measured brightness temperature. In order to determine the surface emissivity of sea ice, the observations of the microwave instruments amsu (Advanced Microwave Sounding Unit) and amsr-e (Advanced Microwave Scanning Radiometer- Earth Observing System) are used. Determination of emissivity requires the knowledge of the temperature of the emitting layer. The penetration depth of microwaves in sea ice varies between millimeters and decimeters depending on the frequency and micro-physical structure. A year-round observation of temperature profiles of sea ice from the Surface Heat Budget of the Arctic Ocean (sheba) campaign at a first-year and a multiyear ice site is used to derive a set of coefficients a and b to linearly relate ...
    Description: thesis
    Keywords: 551.343 ; VAQ 990 ; VAQ 100 ; Meereis {Glaziologie} ; Gletscheruntersuchungen im Allgemeinen
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 22
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 23
    facet.materialart.
    Unknown
    Microbial ecology of anaerobic carbon mineralization in Namibian shelf sediments (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Carbon, Upwelling, Namibia, shelf, sediments. - This PhD thesis is an essential component of the 'Namibia Gas' (NAMIBGAS) project, which aims to improve the understanding of the rate and fluxes of hydrogen sulfide and methane to the sediment surface and into the water column on the Namibian shelf, which is one of the most productive upwelling systems on Earth. Organic matter degradation in the sediment drives hydrogen sulfide production, the maintenance of anoxia, and methane formation. Therefore, the primary aims of the thesis are to study carbon transformation processes within the sediment, determine the reactivity of organic carbon in the sediment and, investigate the control of microbial community structure and activity by the amount and accessibility of carbon sources. The emphasis is on linking microbial community structure (identity) to their function (activity) to provide new insights into the microbial ecology that controls carbon turnover in these upwelling sediments. By studying the stepwise degradation of organic carbon a complete process overview of organic carbon mineralization could be obtained. Firstly, the diagenetic transformation of dissolved organic carbon (DOC), in particular dissolved carbohydrates, was studied by using both biogeochemical methods and molecular techniques. The bulk sediment composition, pore water chemistry, polysaccharide hydrolysis rates, 35S-sulfate reduction rates, and the abundance of active bacteria involved in the initial and terminal processes of organic carbon degradation within the top 15 cm of the sediment from two sampling stations were determined (Chapter 2). Secondly, the diversity of bacteria from the same ...
    Description: thesis
    Keywords: 551 ; VAT 270 ; VGE 500 ; Flachsee-Sedimente {Geologie} ; Biomineralisation
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 24
    facet.materialart.
    Unknown
    High-resolution climate reconstruction for the holocene based on growth chronologies of the bivalve Arctica Islandica from the North Sea (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: High-resolution climate reconstruction, North Sea, annual banded proxy, Arctica islandica. - Until now, there has been no published documentation of North Sea year-to-year climate variability during the last 8000 to 10000 years. High-resolution instrumental time series of climatic and environmental data for the North Sea and the adjacent North Atlantic are only available for the last decades or a century at best. Long term paleoclimatic reconstructions in higher latitudes have been predominantly undertaken using land-based annually banded archives, such as trees, varves, glaciers, and speleothems. A suitable long-term environmental archive with annual may be provided by CaCO3-skeletons of long-lived marine invertebrates. This study evaluates whether recent and subfossil shells of the long-lived bivalve Arctica islandica from the North Sea carry feasible information on Holocene climatic and oceanographic conditions. I compared modern shells of Arctica islandica from two very different habitats, a near-coastal shallow site (German Bight) and a northerly, more central, deep site (Fladen Ground). From the latter, subfossil shells were analysed, also. This study demonstrates that Arctica from both sites provides suitable archives of marine environmental conditions in the form of (i) variations in annual shell ...
    Description: thesis
    Keywords: 560 ; TWC 500 ; VAR 990 ; VXM 200 ; VZZ 120 ; Klimaschwankungen und Klimaänderungen im Quartär ; Meeresräume {Glazialgeologie} ; Lamellibranchiata {Paläozoologie} ; Randmeere {Paläontologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 25
    facet.materialart.
    Unknown
    The role of mesozooplankton grazing in the biogeochemical cycle of silicon in the Southern Ocean (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Calanus simillimus, Rhincalanus gigas, grazing, biogeochemistry, biogenic silica. - The role of copepod grazing, particularly of Calanus simillimus and Rhincalanus gigas, in the biogeochemical cycles of silicon (Si) and carbon (C) in the Antarctic Circumpolar Current (ACC) of the Southern Ocean is investigated. The two grazers show differences in feeding behavior before and in response to a diatom bloom stimulated by in situ iron fertilization. The continuously high feeding activity of C. simillimus on diatoms is conducive to enhance the export of primary produced C and Si. The grazing impact of this key species is high enough to influence population dynamics in the microplankton communities of the ACC. In the pre-bloom situation, R. gigas fulfils most of its carbon requirement through grazing on detritus and thereby effectively reduces the vertical fecal flux produced by C. simillimus. It is proposed that a Copepod-Retention-System for organic material is put in place by the copepod community under High Nutrient Low Chlorophyll (HNLC) conditions. Prey switching by R. gigas from detritus to diatoms in the bloom situation lifts the grazing check on the detritus flux and enables loss of particulate C and Si from the surface layer with fast sinking fecal pellets. Results from dissolution experiments indicate that the enclosure of biogenic silica (BSi) in copepod fecal pellets prevents the dissolution of diatom frustules. Diatoms submitted to grazing of copepods and krill (Euphausia superba) dissolved 4 to 26 times slower than un-grazed controls.
    Description: thesis
    Keywords: 560 ; VJE 220 ; Geochemie der Fauna
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 26
    facet.materialart.
    Unknown
    Magmatic and volcanological evolution of the Desertas rift zone (Madeira Archipelago, NE Atlantic) (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Volcanology, volcanic rift zones, Madeira, fluid inclusions, thermobarometry, geochemistry, geochronology. - Madeira and the Desertas Islands show two well-developed volcanic rift zones which intersect near the eastern tip of Madeira (São Lourenço peninsula). To examine a possible genetic link, volcanic structures, rock ages and rock compositions were investigated at the Desertas and São Lourenço. Barometric data derived from fluid inclusions and clinopyroxene-melt compositions indicate fractionation at multiple levels within the mantle beneath the rift zones, followed by temporary magma stagnation within the crust. Depths of crustal stagnation beneath São Lourenço and the Desertas differ significantly, and there is no evidence for a shallow magma reservoir feeding both rifts. This suggests that Madeira and the Desertas have separated magma supply systems. 40Ar/39Ar age determinations revealed that Desertas volcanism lasted from 〉5.1 to 1.9 Ma overlapping in age with the shield phase of Madeira. Eruptive quiescence between 4 and 2.5 Ma at São Lourenço coincides with the main period of volcanism on the Desertas. Major and trace elements and ...
    Description: thesis
    Keywords: 551 ; VAD 600 ; VAD 700 ; VAE 840 ; VEF 139 ; Paläovulkanismus {Geologie} ; Regionaler Vulkanismus {Geologie} ; Rifts {Geologie} ; Balearen un Pityusen {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 27
    facet.materialart.
    Unknown
    Modeling physical and biological processes in Antarctic sea ice (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VAQ 990 ; Meereis {Glaziologie}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 28
    facet.materialart.
    Unknown
    Seasonal dynamics and characterization of coccolithophore export production in two major upwelling regions (2010)
    Univ. Bremen
    Details
    Publication Date: 2020-10-05
    Description: Coccolithophores, a major group of the nanophytoplankton, belong to the class Prymnesiophyceae.The cells of coccolithophores are typically surrounded by layer(s) of calcium carbonate plates, the coccoliths. Certain coccolithophores can be assigned to particular water masses or to photic zone characteristics and, therefore, single species as well as whole assemblages can be used as oceanographical indicators for the present and the past. Due to their ocean wide distribution, their large contribution to the fine grained carbonate ooze of the deep sea, their ability to photosynthesize and to calcificate they play an important role in the global carbon cycle...
    Description: thesis
    Keywords: 579.17 ; 577.7 ; 577.15 ; 579.82 ; 560 ; VJI 000 ; VU 000 ; VU 000 ; VJI 000 ; Geobiologie ; Geochemische Kreislaufmodelle
    Language: English
    Type: monograph , publishedVersion
    Format: 151 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 29
    facet.materialart.
    Unknown
    Reconstruction of astronomically forced cyclic and abrupt palaeoecological changes in the upper cretaceous boreal realm based on calcareous dinoflagellate cysts (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 560 ; TWC 600 ; VYF 200 ; VYA 500 ; VWH 300 ; VDH 320 ; Paläoklimatologie ; Pyrrophyceae {Paläobotanik} ; Paläökologie {Paläobotanik} ; Kreide {Stratigraphische Paläontologie} ; Oberkreide
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 30
    facet.materialart.
    Unknown
    Modelling the marine carbonate pump and its implications on the atmospheric CO2 concentration (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The marine carbonate pump includes the production of calcium carbonate, CaCO3 by marine organisms and its subsequent transport to depth. The balance between carbonate production in surface waters and dissolution and accumulation in sediments influences the surface water CO2 concentration and thus the oceanś capacity to take up atmospheric CO2.Models are developed to investigate on calcium carbonate dissolution in the oceanic water column. Model results yield that dissolution in zooplankton guts contributes a significant portion of the proposed carbonate loss. Dissolution fueled by the respiration of organic matter in marine snow aggregates is very sensitive to the size and settling velocity of the aggregate, which determines the boundary layer thickness and the stability of an undersaturated microenvironment. The constraints set by field data yield that the chemical gradients between the aggregate and the bulk seawater are too small to enable significant carbonate dissolution. Furthermore, the role of the carbonate pump in regulating atmospheric pCO2 on glacial to interglacial timescales is investigated ...
    Description: thesis
    Keywords: 551.9 ; VJI 000 ; Geochemische Kreislaufmodelle
    Language: English
    Type: monograph , publishedVersion
    Format: 132 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 31
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 32
    facet.materialart.
    Unknown
    Deformation and micromechanics of granular materials in shear zones - investigated with the Discrete Element Method (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Deformation, shear zone, granular, micromechanic, numerical model, discrete element method, distinct element method. - This thesis was inspired by the lack of detailed (i.e. particle scale) knowledge concerning deformation processes of mechanically weak sediments, especially intrinsically weak layers on the basal shear plane of submarine landslides. It has been known for some time that many different parameters influence shear strength and localization features. This is true not only for sediments, but also for other kinds of weak layers, such as fault gouge. These parameters include for example mineralogy (e.g. smectite, illite, quartz), sediment composition (clay, silt), sediment structure and texture (microfabric), grain size distribution, excess pore pressure, magnitude of effective stress, and deformation history. However, to date it has not been possible to rank or to quantify the influence of each of these parameters. The main goal of this study is to analyze the influence of some of these parameters and, if possible, rank and quantify them. Standard methods to examine shear strength of sediments and fault gouge are various geotechnical shear experiments. In these, a sample is sheared under defined conditions and resulting coefficient of friction, void ratio change, and other meaningful parameters are analyzed. Unfortunately, it is not possible to 'look' inside a shear box during a test and to analyze grain deformation behaviour on a microscopic scale. Therefore, this study employs a different approach to specifically address the problem of microscopic deformation processes. Here, a numerical modelling technique, the Discrete Element Method (DEM), is used. The DEM is a numerical tool based on the ...
    Description: thesis
    Keywords: 551.8 ; VAE 130 ; VAE 130 ; Geomechanik
    Language: English
    Type: monograph , publishedVersion
    Format: 138 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 33
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 34
    facet.materialart.
    Unknown
    Tectonic and magmatic processes along the transform margin of Southern Africa (2010)
    Univ. Bremen
    Details
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 35
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 36
    facet.materialart.
    Unknown
    Crustal structure modelling and interpretation of the East Greenland continental margin between 72°N and 77°N (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Integrated studies of conjugate margins provide important constraints for the sequence of events of synrift tectonic and magmatic processes. The northeast Greenland margin is investigated based on seismic refraction data acquired across the continent ocean transition zone between the Jan Mayen and Greenland fracture zones. Transects of seismic velocity models reveal a clear segmentation of the margin, which is compatible with the potential field data. A crucially important observation is a thick high velocity lower crustal body which clearly decreases northwards. Excessive magmatism is inferred to have occurred during long-term rifting in the south, while reduced syn-rift intrusions account for the norhtern magma-starved margin. Asymmetries and variations across the adjacent and conjugate East Greenland and Norwegian margins, are controversially discussed in terms of the origin of the lower crustal body and magnetic spreading anomalies. Three hypothetical scenarios for the timing and formation of the high velocity lower crustal body are presented. A comprehensive subsidence analysis is established which quantifies the amount of magmatic underplating.
    Description: thesis
    Keywords: 551.136 ; VAE 880 ; TSY 100 ; VBM 000 ; VAE 880 ; TSY 100 ; VBM 000 ; Passive und aktive Kontinentalränder {Geologie} ; Arktis {Geophysik} ; Geologische Interpretation geophysikalischer Beobachtungen
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 37
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 38
    facet.materialart.
    Unknown
    Polarimetric remote sensing of land and snow/ice covers with the Spaceborne Microwave Radiometer WindSat (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Microwave remote sensing, polarimetry, radiometer, WindSat, passive. - Measurements from spaceborne microwave radiometers, such as the Scanning Multichannel Microwave Radiometer (SMMR), the Special Sensor Microwave/Imager (SSM/I) and the Advanced Microwave Scanning Radiometer (AMSR), are found to be useful in estimating various earth surface geophysical quantities, e.g. soil moisture and vegetation characteristics over land, snow water equivalent for snow covers and sea ice concentration. All these instruments have measured only the vertical and horizontal polarization component of the brightness temperature (Tb ). WindSat is the first spaceborne radiometer to provide fully polarimetric measurements of the earthÃ
    Description: thesis
    Keywords: 551.5 ; TUA 800 ; TVK 100 ; Radarmeteorologie ; Windmessungen und Beobachtungsergebnisse im Allg. {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 122 S.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 39
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 40
    facet.materialart.
    Unknown
    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.
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 41
    facet.materialart.
    Unknown
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 42
    facet.materialart.
    Unknown
    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
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 43
    facet.materialart.
    Unknown
    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
    Type: monograph , publishedVersion
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 44
    facet.materialart.
    Unknown
    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
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...