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Müller, H; von Dobeneck, Tilo; Hilgenfeldt, Christian; SanFelipo, Bill; Rey, Daniel; Rubio, Belen (2012): Magnetic susceptibility and electric conductivity of marine surficial sediments by benthic electromagnetic profiling. PANGAEA, https://doi.org/10.1594/PANGAEA.776056, Supplement to: Müller, H et al. (2012): Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling. Geophysics, 77(1), E43-E56, https://doi.org/10.1190/GEO2010-0129.1

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Abstract:
Distribution, accumulation and diagenesis of surficial sediments in coastal and continental shelf systems follow complex chains of localized processes and form deposits of great spatial variability. Given the environmental and economic relevance of ocean margins, there is growing need for innovative geophysical exploration methods to characterize seafloor sediments by more than acoustic properties. A newly conceptualized benthic profiling and data processing approach based on controlled source electromagnetic (CSEM) imaging permits to coevally quantify the magnetic susceptibility and the electric conductivity of shallow marine deposits. The two physical properties differ fundamentally insofar as magnetic susceptibility mostly assesses solid particle characteristics such as terrigenous or iron mineral content, redox state and contamination level, while electric conductivity primarily relates to the fluid-filled pore space and detects salinity, porosity and grain-size variations. We develop and validate a layered half-space inversion algorithm for submarine multifrequency CSEM with concentric sensor configuration. Guided by results of modeling, we modified a commercial land CSEM sensor for submarine application, which was mounted into a nonconductive and nonmagnetic bottom-towed sled. This benthic EM profiler Neridis II achieves 25 soundings/second at 3-4 knots over continuous profiles of up to hundred kilometers. Magnetic susceptibility is determined from the 75 Hz in-phase response (90% signal originates from the top 50 cm), while electric conductivity is derived from the 5 kHz out-of-phase (quadrature) component (90% signal from the top 92 cm). Exemplary survey data from the north-west Iberian margin underline the excellent sensitivity, functionality and robustness of the system in littoral (~0-50 m) and neritic (~50-300 m) environments. Susceptibility vs. porosity cross-plots successfully identify known lithofacies units and their transitions. All presently available data indicate an eminent potential of CSEM profiling for assessing the complex distribution of shallow marine surficial sediments and for revealing climatic, hydrodynamic, diagenetic and anthropogenic factors governing their formation.
Keyword(s):
apparent resistivity; electromagnetics; magnetic susceptibility; mapping; marine sediments
Coverage:
Median Latitude: 42.066162 * Median Longitude: -9.128179 * South-bound Latitude: 41.964793 * West-bound Longitude: -9.374029 * North-bound Latitude: 42.166935 * East-bound Longitude: -8.974898
Date/Time Start: 2008-06-05T00:00:00 * Date/Time End: 2008-06-17T00:00:00
Event(s):
GeoB130106 * Latitude Start: 41.965975 * Longitude Start: -9.189123 * Latitude End: 41.965975 * Longitude End: -8.991927 * Date/Time Start: 2008-06-05T00:00:00 * Date/Time End: 2008-06-05T00:00:00 * Campaign: POS366/3 * Basis: Poseidon * Method/Device: EM Profiler, NERIDIS II (NER-II) * Comment: course 90°
GeoB130124 * Latitude Start: 42.165871 * Longitude Start: -9.396215 * Latitude End: 42.166904 * Longitude End: -8.967189 * Date/Time: 2008-06-17T00:00:00 * Campaign: POS366/3 * Basis: Poseidon * Method/Device: EM Profiler, NERIDIS II (NER-II) * Comment: course 90°
Size:
15 datasets

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Datasets listed in this publication series

  1. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 10a, 11, 12) Benthic electromagnetic profile of GeoB130124 on the northwest Iberian shelf. https://doi.org/10.1594/PANGAEA.776054
  2. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 10b, 11) Benthic electromagnetic profile of GeoB130106 on the northwest Iberian shelf. https://doi.org/10.1594/PANGAEA.776055
  3. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 2) Primary magnetic field intensity distribution of EM sensor. https://doi.org/10.1594/PANGAEA.775956
  4. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 3) Modeled GEM-3 susceptibility and conductivity response under decreasing water depth. https://doi.org/10.1594/PANGAEA.775957
  5. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 4a) Relative contribution of the magnetic response to total in-phase signal in function of EM field frequency, sediment susceptibility and conductivity. https://doi.org/10.1594/PANGAEA.775960
  6. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 4b) Frequency-dependence of inphase and quadrature conductivity noise floor. https://doi.org/10.1594/PANGAEA.775961
  7. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 5a) Vertical sensor characteristics of GEM-3 (96 cm coil) for in-phase susceptibility. https://doi.org/10.1594/PANGAEA.775963
  8. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 5b) Vertical sensor characteristics of GEM-3 (96 cm coil) for quadrature conductivity given as weighting functions and cumulative subsurface response. https://doi.org/10.1594/PANGAEA.775970
  9. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 5c) In-phase and quadrature responses of GEM-3 sensor at various operation frequencies. https://doi.org/10.1594/PANGAEA.775976
  10. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 6a) Lateral response of GEM-3 sensor (96 cm coil) for susceptibility and 5 kHz quadrature conductivity on homogeneous seafloor. https://doi.org/10.1594/PANGAEA.776000
  11. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 6b) Horizontal footprint diameter (90% of the total signal) and half-width (50%) of susceptibility, quadrature and in-phase conductivity. https://doi.org/10.1594/PANGAEA.776005
  12. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 7a) Simulations of apparent susceptibility and conductivity profiles of a dipping mud/sand boundary. https://doi.org/10.1594/PANGAEA.776006
  13. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 7b) Apparent susceptibility profiles by various available sensor sizes of dipping sulfidic (magnetite-reducing) zone. https://doi.org/10.1594/PANGAEA.776009
  14. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 9a) Correlation of EM and sediment core porosity. https://doi.org/10.1594/PANGAEA.776011
  15. Müller, H; von Dobeneck, T; Hilgenfeldt, C et al. (2012): (Figure 9b) Correlation of EM and sediment core susceptibility. https://doi.org/10.1594/PANGAEA.776012