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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic domain observations on magnetite and titanomaghemite grains (0.5–10 μm) (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: By using the Bitter method, we have observed the magnetic domain structures of natural titanomaghemite grains and magnetite crystals (0.5–10 μm) that were grown in a glass ceramic matrix. The observations were carried out in a range of applied magnetic fields and were correlated to the hysteresis properties of the bulk samples. Our observations show that simple, lamellar structures cannot explain the high-field hysteresis behaviour in either the titanomaghemite or the magnetite sample. This high-field behaviour is probably dominated by complicated, stress-influenced domain structures and rotation processes. A plot of the number of lamellar domains observed in magnetite grains versus their grain size yields a single-domain to two-domain transition size of 0.25 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06353.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Three-dimensional micromagnetic calculations for magnetite using FFT (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An unconstrained 3-D micromagnetic model for magnetite grains with resolutions up to 23 × 23 × 63 is presented. The model has been used to investigate the magnetic domain states of submicron parallelepipeds with various elongations. The method of fast Fourier transformation (FFT) has been implemented in three dimensions to accelerate the computation of the magnetostatic energy and its gradient, assuming constant magnetization for each subcube of the model. A 3-D implementation of the exchange energy and its gradient, using a five-point formula to approximate the Laplace operator, was chosen. Special attention has been paid to single-domain (SD) or flower states and pseudo-single-domain (PSD) configurations. A circular configuration, called vortex state, has been found to have the lowest energy of various PSD states. As a local energy minimum (LEM), the free energy of the vortex state is compared to that of a single-domain state. A comparison of these energies is used to determine a lower and an upper threshold size for the SD to PSD transition. In the interval between these two threshold sizes both configurations, SD and PSD, coexist. Above the upper threshold size we found metastable double-vortex configurations which seem to represent three-domain structures with closure domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06354.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Kapitulationsproblem und knotentheorie (1984)
    Springer
    Manuscripta mathematica 46 (1984), S. 229-272 
    Details
    ISSN: 1432-1785
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The capitulation problem concerns the determination of the transfer-kernel Ke((G(L¦k)ab→G(L¦K)ab) for Galois field towers L¦K¦k in certain classformations of number fields. 3 special instances are dealt with: (1) The capitulation kernel can be described in terms of ray knots if L is a ray class field over K. (2) lyanaga's application of the genus conductor is extended to the non-abelian case. (3) The cohomology of the S-idel class group of the maximal extension of k unramified outside a finite set S ⊃ S∞ of primes can be expressed by the cohomology of the S-Leopoldt-kernel. This leads to a description of the respective capitulation kernel and moreover of the Schur multiplier of the Galois group of the maximal p-extension unramified outside p (p≠2) in terms of the usual Leopoldt-kernel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185203
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  • 4
    Electronic Resource
    Electronic Resource
    Zahlentheoretische Knoten unendlicher Erweiterungen (1981)
    Springer
    Archiv der Mathematik 37 (1981), S. 341-352 
    Details
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01234367
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  • 5
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    Chemobiostratigraphy of the Cretaceous/Paleocene boundary at ODP Hole 120-750A (1992)
    PANGAEA
    In:  Supplement to: Zachos, James C; Aubry, Marie-Pierre; Berggren, William A; Ehrendorfer, Thomas; Heider, Franz; Lohmann, Kyger C (1992): Chemobiostratigraphy of the Cretaceous/Paleocene boundary at Site 750, Southern Kerguelen Plateau. In: Wise, SW; Schlich, R; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 120, 961-977, https://doi.org/10.2973/odp.proc.sr.120.188.1992
    Details
    Publication Date: 2024-01-09
    Description: An integrated biostratigraphic and stable isotope investigation was conducted on a high-latitude sequence across the Cretaceous/Paleogene (K/P) boundary recovered in Hole 750A in the southern Indian Ocean. The sequence consists of nannofossil chalk and is discontinuous across the boundary; missing is an estimated 0.3-m.y. late Maestrichtian and early Danian interval. Nonetheless, because calcareous nannofossil Zones NP1 and NP2 are well-developed, micropaleontological studies of the sequence have yielded a detailed record of Danian high-latitude microplankton evolution. In addition, stable carbon isotope analyses of planktonic and benthic foraminifer and bulk samples provide a record of late Maestrichtian and early Danian surface- and deep-water carbon isotope variations. Together, the carbon isotope and carbonate accumulation records serve as an index of regional marine net productivity across the boundary. Earliest Danian nannoplankton assemblages consisted mainly of persistent genera that were generally rare or absent in the Upper Cretaceous at Hole 750A. However, by 0.5-0.6 m.y. after the boundary, newly evolving Danian taxa became dominant. The turnover in nannofossil assemblages was accompanied by significant changes in rates of net productivity as gauged by carbon isotope distributions and carbonate accumulation rates. During the period dominated by persistent taxa, net productivity was extremely low, as reflected by the absence of vertical delta13C gradients and reduced carbonate accumulation rates. Later in the Danian, as new species evolved and flourished, vertical delta13C gradients reappeared and carbonate accumulation rates increased, signaling partial recovery of net productivity in this region. The absolute timing and magnitude of late Maestrichtian and early Danian biotic and geochemical changes in the southern Indian Ocean were similar to those recorded in other pelagic K/P boundary sequences from low- and mid-latitude Atlantic and Pacific sites, indicating that these events were ubiquitous.
    Keywords: 120-750A; DRILL; Drilling/drill rig; Joides Resolution; Leg120; Ocean Drilling Program; ODP; South Indian Ridge, South Indian Ocean
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 6
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    Magnetostratigraphy of ODP Hole 157-953C (Table 1) (2003)
    PANGAEA
    In:  Supplement to: Herr, B; Fuller, Michael D; Sumita, Mari; van den Bogaard, Paul; Schmincke, Hans-Ulrich; Heider, Franz (2003): New tie-points for the geomagnetic polarity time scale during the Middle Miocene from the Mogán Group on Gran Canaria and Ocean Drilling Program Leg 157 site 953. International Journal of Earth Sciences, 91(4), 642-660, https://doi.org/10.1007/s00531-001-0255-6
    Details
    Publication Date: 2024-01-09
    Description: A thick sequence of volcaniclastic sediments drilled at site 953 during Ocean Drilling Program (ODP) Leg 157 northeast of Gran Canaria (Canary Islands) contains an almost complete magneto-stratigraphy back to the shield stage of the island 14.8 Ma ago. Onshore, a sequence of reversals has been identified and dated in 19 dominantly peralkaline rhyolitic ignimbrites, one rhyolitic, and one basaltic lava flow of the Mogán Group (13.35-13.95 Ma), which overlie basalt flows of the island's shield stage (〉14 Ma). The magneto-stratigraphy of the ignimbrites onshore has been correlated with the marine magneto-stratigraphy at site 953, determined in syn-ignimbritic volcaniclastic turbidites, which were deposited practically synchronously immediately following the entry of the parent pyroclastic flows into the sea around the circumference of the island. The four polarity intervals recorded in the sequence of the Mogán Group ignimbrites correspond to C5ACr, C5ACn, C5ADr and C5ADn. Single crystal 40Ar/39Ar-age determinations of the ignimbrites bracketing the polarity changes gave the following ages and uncertainties for the reversals C5AD(t) (13.95±0.07 Ma), C5AC(o) (13.89±0.08 Ma), and C5AC(t) (13.47±0.09 Ma). The newly dated polarity changes fit and refine the Miocene age model proposed in the global polarity time scale.
    Keywords: 157-953C; Age, dated; Age, paleomagnetic; Canarias Sea; Chronozone; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Joides Resolution; Leg157; Magnetometer, cryogenic; Ocean Drilling Program; ODP; Sample code/label; Sample code/label 2
    Type: Dataset
    Format: text/tab-separated-values, 184 data points
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  • 7
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    Curie temperatures and cell edges of ODP Leg 120 samples (Table 1) (1992)
    PANGAEA
    In:  Supplement to: Heider, Franz; Geiss, Christoph; Dunlop, David J; Inokuchi, Hiroo (1992): Rock-Magnetic investigation of basalts from the southern Kerguelen Plateau (Leg 120). In: Wise, SW; Schlich, R; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 120, 79-87, https://doi.org/10.2973/odp.proc.sr.120.127.1992
    Details
    Publication Date: 2024-01-09
    Description: Basalt samples recovered on Ocean Drilling Program Leg 120 from the Kerguelen Plateau were investigated by thermomagnetic analysis, X-ray diffraction, and ore microscopy. The basement samples could be divided into two groups based on Curie temperatures, cell-edge parameters, and optical magnetic mineralogy. Samples from Sites 748 and 750 underwent only low-temperature oxidation and displayed Curie temperatures for the titanomaghemites that ranged from 340° to 395°C. The basalts from Sites 747 and 749 mainly experienced high-temperature oxidation. High-temperature oxidation produced titanium-poor titanomagnetites with ilmenite-exsolution lamellae. Curie temperatures of the deuterically oxidized titanomaghemites varied from 490° to 620°C.
    Keywords: -; 120-747C; 120-748C; 120-749C; 120-750B; Alteration; Comment; Curie temperature; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Joides Resolution; Leg120; Number; Ocean Drilling Program; ODP; Sample code/label; South Indian Ridge, South Indian Ocean; Standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 150 data points
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    DATA PANGAEA
  • 8
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    Paleomagnetic of basalts from the Kerguelen Plateau (1992)
    PANGAEA
    In:  Supplement to: Inokuchi, Hiroo; Heider, Franz (1992): Paleolatitude of the southern Kerguelen Plateau inferred from the paleomagnetic study of late Cretaceous basalts. In: Wise, SW; Schlich, R; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 120, 89-96, https://doi.org/10.2973/odp.proc.sr.120.129.1992
    Details
    Publication Date: 2024-01-09
    Description: Paleomagnetic measurements were performed on 106 basalt samples collected from Holes 747C, 748C, 749C, and 750B. Basalt samples were recovered from the southern portion of the Kerguelen Plateau and the transitional zone between the northern and southern plateau in the south central Indian Ocean. The ages of basalts range from 100 to 115 Ma. In addition to the preliminary shipboard measurements (Schlich, Wise, et al., 1989, doi:10.2973/odp.proc.ir.120.1989), characteristic inclinations of the magnetization were obtained using mainly stepwise thermal demagnetization of the samples. Reliable paleomagnetic results were obtained from three sites (Sites 747, 748, and 749). The paleomagnetic inclinations of Sites 747, 748, and 749 are -51°, -63°, and -62°, respectively. The considerable differences between the paleomagnetic and present inclinations of about 70° at Sites 747, 748, and 749 indicate that displacement in the direction of the geomagnetic meridian has taken place since formation of the basalt. Shallower paleomagnetic inclinations than the present inclinations at each site imply a southward movement of the sites with respect to the geomagnetic pole. By comparing the apparent polar wander path of Antarctica with the virtual geomagnetic pole (VGP) of the Southern Kerguelen Plateau, we have concluded that no major tectonic movement has taken place between the Kerguelen Plateau and Antarctica since formation of the basalt (i.e., 100-115 Ma). The angular dispersion of the VGP for the Kerguelen Plateau is calculated as 17°.
    Keywords: 120-747C; 120-748C; 120-749C; 120-750B; Demagnetization step; Demag Type; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Joides Resolution; Leg120; NRM, Inclination; NRM, Inclination after demagnetization; NRM, Intensity; Ocean Drilling Program; ODP; Sample code/label; South Indian Ridge, South Indian Ocean
    Type: Dataset
    Format: text/tab-separated-values, 612 data points
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    DATA PANGAEA
  • 9
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    Magnetic and petrographic properties of ODP Site 120-747 (Table 1) (1993)
    PANGAEA
    In:  Supplement to: Heider, Franz; Körner, Ulrike; Bitschene, Peter Rene (1993): Volcanic ash particles as carriers of remanent magnetization in deep-sea sediments from the Kerguelen Plateau. Earth and Planetary Science Letters, 118(1-4), 121-134, https://doi.org/10.1016/0012-821X(93)90163-4
    Details
    Publication Date: 2024-01-09
    Description: Carbonate sediments from the Kerguelen Plateau (ODP Leg 120) of Eocene to Pliocene age were investigated with rock magnetic, petrographic and geochemical methods to determine the carriers of remanent magnetization. Magnetic methods showed that the major magnetic minerals were titanomagnetites slightly larger than single domain particles. Submicrometre to micrometre-size grains of titanomagnetite were identified as inclusions in volcanic glass particles or as crystals in lithic clasts. Volcanic fallout ash particles formed the major fraction of the magnetic extract from each sediment sample. Three groups of volcanic ashes were identified: trachytic ashes, basaltic ashes with sideromelane and tachylite shards, and palagonitic ashes. These three groups could be equally well defined based on their magnetic hysteresis properties and alternating field demagnetization curves. The highest coercivities of all samples were found for the tachylite, due to the submicrometre-size titanomagnetite inclusions in the matrix. Trachytic ashes had intermediate magnetic properties between the single-domain-type tachylites and the palagonitic (altered) basaltic ashes with low coercivities. Samples which contained mixtures of these different volcanic ashes could be distinguished from the three types of ashes based on their magnetic characteristics. There was neither evidence of biogenic magnetofossils in the transmission electron micrographs nor did we find magnetic particles derived from continental Antarctica. The presence of dispersed volcanic fallout ashes between visible ash layers suggests continuous explosive volcanic activity on the Kerguelen Plateau in the South Indian Ocean since the early Eocene. The continuous fallout of volcanic ash from explosive volcanism on the Kerguelen Archipelago is the source of the magnetic particles and thus responsible for the magnetostratigraphy of the nannofossil oozes drilled during Leg 120.
    Keywords: -; 120-747; COMPCORE; Composite Core; DEPTH, sediment/rock; DSDP/ODP/IODP sample designation; Hysteresis, Bcr/Bc; Hysteresis, coercive field; Hysteresis, remanent coercive field; Hysteresis, saturation magnetization/ saturation remanence; IRM, median destructive field of isothermal remanent magnetization; Joides Resolution; Leg120; Lithology/composition/facies; Magnetic susceptibility, volume; Ocean Drilling Program; ODP; Sample code/label; Sample code/label 2; Sample comment; Saturation isothermal remanent magnetisation; South Indian Ridge, South Indian Ocean
    Type: Dataset
    Format: text/tab-separated-values, 180 data points
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  • 10
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    (Table 2) Age model control points, and CaCO3 and TOC accumulation rates of ODP Leg 167 sites (1997)
    PANGAEA
    In:  Supplement to: Ravelo, Ana Christina; Lyle, Mitchell W; Koizumi, Itaru; Caulet, Jean-Pierre; Fornaciari, Eliana; Hayashida, Akira; Heider, Franz; Hood, Julie A; Hovan, Steven A; Janecek, Thomas R; Janik, Aleksandra G; Stax, Rainer (1997): Pliocene carbonate accumulation along the California Margin. Paleoceanography, 12(6), 729-741, https://doi.org/10.1029/97PA02525
    Details
    Publication Date: 2024-01-09
    Description: Recent modeling studies call on increased ocean heat transport to explain high-latitude warming observed for intervals throughout the middle Pliocene. Possible vehicles for ocean heat transport are the poleward arms of the subtropical gyres. Sites from the California margin (Ocean Drilling Program Leg 167) provide monitors of wind field within the eastern arm of the gyre which may be an indication of basin-wide subtropical gyral strength. At most sites (water depths from 1106 to 4212 m) CaCO3 mass accumulation rate (MAR) was highest in the middle Pliocene (3.5-2.0 Ma). This high CaCO3 MAR 'event' is attributed primarily to higher CaCO3 production due to higher offshore upwelling associated with the zone of the greatest wind stress curl. Thus, in the middle Pliocene, there was enhanced wind stress curl along the California margin, and possibly enhanced North Pacific sub-tropical gyral circulation and meridional ocean heat advection.
    Keywords: 167-1010; 167-1011; 167-1012; 167-1013; 167-1014; 167-1016; 167-1017; 167-1018; 167-1019; 167-1020; 167-1021; Accumulation rate, calcium carbonate; Accumulation rate, total organic carbon; AGE; Age, maximum/old; Age model; Ageprofile Datum Description; Calcium carbonate; Carbon, organic, total; COMPCORE; Composite Core; Density, dry bulk; Depth, composite; Depth, composite bottom; Depth, composite top; DEPTH, sediment/rock; Elevation of event; Event label; Joides Resolution; Latitude of event; Leg167; Longitude of event; North Pacific Ocean; Nuttallides rugosa, δ13C; Ocean Drilling Program; ODP; Sedimentation rate
    Type: Dataset
    Format: text/tab-separated-values, 1353 data points
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