Near-surface electromagnetic, rock magnetic, and geochemical fingerprinting of submarine freshwater seepage at Eckernförde Bay (SW Baltic Sea)

Müller, Hendrik; Dobeneck, Tilo von; Nehmiz, Wiebke; Hamer, Kay

doi:10.1007/s00367-010-0220-0

Cited by 43 publications

(19 citation statements)

References 49 publications

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“…As the conceptual κ and σ profiles of Figure 1 suggest, both parameters offer to some degree related, but also complementary information on various primary and secondary geological processes. Results of a high-resolution survey of freshwater seeps in Eckernförde Bay (SW Baltic Sea) have been published separately (Müller et al, 2011). Therein, we demonstrate that EM profiling, complemented and validated by acoustic, as well as sample-based rock magnetic and geochemical methods, can create a crisp and revealing fingerprint image of freshwater seepage and reductive alteration of near-surface sediments.…”

Section: Introductionmentioning

confidence: 91%

“…The first example addresses sediment distribution in transition regions of mud, siliciclastic sands, and glauconite sands across a 30 km wide section of the northwest Iberian continental shelf in water depths of 50-270 m. The second example from the same region takes a close-up at a 10 km wide bottom-current induced sand wave field on the outer shelf and investigates the relations of bedform morphology and sediment composition. A pilot study on sediment and scrap metal distribution in the Galician Ría de Vigo (Rey et al, 2008) and another, very detailed survey of groundwater seeps in Eckernförde Bay, western Baltic Sea (Müller et al, 2011) are published separately.…”

Section: Applications In Coastal and Continental Shelf Researchmentioning

confidence: 99%

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Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

et al. 2012

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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 a 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 versus porosity crossplots 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.

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Section: Introductionmentioning

confidence: 91%

Section: Applications In Coastal and Continental Shelf Researchmentioning

confidence: 99%

Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

et al. 2012

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“…There are very few EM surveys of areas affected by pockmarks [e.g., Müller et al ., ; Minshull et al ., ; Hsu et al ., ], but some of the conclusions drawn from these works are that shallow EM profiling can significantly improve understanding of sediment distribution and vertical zonation of seepage processes. It has been postulated that the walls of pockmarks act as pathways for gas flow [ Newman et al ., ] and that sediments are disturbed within the pockmark as a consequence of the violent gas release mechanism [ Judd and Hovland , ].…”

Section: Introductionmentioning

confidence: 99%

Constraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland

García

Monteys

Evans

et al. 2014

Geochem. Geophys. Geosyst.

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During the Irish National Seabed Survey (INSS) in 2003, a gas related pockmark field was discovered and extensively mapped in the Malin Shelf region (NW Ireland). In summer 2006, additional complementary data involving core sample analysis, multibeam and single-beam backscatter classification, and a marine controlled-source electromagnetic survey were obtained in specific locations.This multidisciplinary approach allowed us to map the upper 20 m of the seabed in an unprecedented way and to correlate the main geophysical parameters with the geological properties of the seabed. The EM data provide us with information about sediment conductivity, which can be used as a proxy for porosity and also to identify the presence of fluid and fluid migration pathways. We conclude that, as a whole, the central part of the Malin basin is characterized by higher conductivities, which we interpret as a lithological change. Within the basin several areas are characterized by conductive anomalies associated with fluid flow processes and potentially the presence of microbial activity, as suggested by previous work. Pockmark structures show a characteristic electrical signature, with high-conductivity anomalies on the edges and less conductive, homogeneous interiors with several high-conductivity anomalies, potentially associated with gas-driven microbial activity.

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“…The method has also been used to map the spatial distribution and composition of magnetic minerals in the coastal zone, to assess their degree of sorting, and to identify areas of sediment accumulation and erosion Hatfield et al, 2010;Zhang et al, 2010]. The technical ability to resolve magnetite distribution patterns in detail has been improved by the development of benthic electromagnetic profiling, which permits rapid mapping of magnetic susceptibility together with electrical conductivity [Müller et al, 2011[Müller et al, , 2012. This sample-based study is aimed at deepening fundamental understanding of geological and hydrodynamic processes as a prerequisite for future high-resolution mapping and modeling.…”

Section: Introductionmentioning

confidence: 99%

Formation of magnetite‐enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand

Badesab

Dobeneck

Bryan

et al. 2012

Geochem Geophys Geosyst

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[1] Magnetic iron minerals are widespread and indicative sediment constituents in estuarine, coastal and shelf systems. We combine environmental magnetic, sedimentological and numerical methods to identify magnetite-enriched placer-like zones in a complex coastal system and delineate their formation mechanisms. Magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around Tauranga Harbour, the largest barrier-enclosed tidal estuary of New Zealand, reveal several discrete enrichment zones controlled by local hydrodynamic conditions. Active magnetite enrichment takes place in tidal channels, which feed into two coast-parallel nearshore magnetite-enriched belts centered at water depths of 6-10 m and 10-20 m. A close correlation between magnetite content and magnetic grain size was found, where higher susceptibility values are associated within coarser magnetic crystal sizes. Two key mechanisms for magnetite enrichment are identified. First, tide-induced residual currents primarily enable magnetite enrichment within the estuarine channel network. A coast-parallel, fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite ©2012. American Geophysical Union. All Rights Reserved.1 of 20 content away from the southern tidal inlet and is apparently related to active coast-parallel transport combined with mobilizing surf zone processes. A second, less pronounced, but more uniform magnetite enrichment belt at 10-20 m water depth is composed of non-mobile, medium-coarse-grained relict sands, which have been reworked during post-glacial sea level transgression. We demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms.

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Near-surface electromagnetic, rock magnetic, and geochemical fingerprinting of submarine freshwater seepage at Eckernförde Bay (SW Baltic Sea)

Cited by 43 publications

References 49 publications

Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

Constraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland

Formation of magnetite‐enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand

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