Use of environmental magnetic measurements to validate the vertical extent of ice masses at the Last Glacial Maximum

Walden, John; Ballantyne, Colin K.

doi:10.1002/jqs.666

Cited by 24 publications

(18 citation statements)

References 23 publications

(34 reference statements)

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“…haematite and goethite) within the sample (e.g. Walden and Ballantyne, 2002). Samples from profile 3 showed the highest values for this parameter, thus a dominant antiferromagnetic component is expected in these samples.…”

Section: Magnetic and Sem/eds Analysesmentioning

confidence: 94%

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

et al. 2014

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This study presents an application of environmental magnetism techniques for the characterisation of the soils near Coimbra (central Portugal). Magnetic measurements, scanning electron microscopy and geochemical studies were carried out on samples collected in 6 soil profiles in order to find possible relationships and to interpret environmental implications. Magnetic susceptibility, saturation isothermal remanent magnetisation and isothermal remanent magnetisation at the backfield of 100 mT and 300 mT were measured. HardIRM %, SIRM/χ and S-ratios were also calculated. Polluted soils showed higher values of magnetic parameters in the superficial soil horizons closer to the roads, plants and urban areas. The lowest values were observed in the deeper horizons of the soil and in the areas least disturbed by human activity. The magnetic results also suggested that the magnetic signal of these soils is mainly influenced by ferrimagnetic magnetite-like minerals and with only a minor contribution from antiferromagnetic carriers (such as hematite minerals). In unpolluted soils, lithogenic contribution is reflected by the enhancement of magnetic susceptibility near parental rock material. Scanning electron microscope images of the topsoil samples revealed the presence of magnetic spherules typical of vehicular exhaust and combustion processes. This evidence suggests that the atmospheric deposition of fly ash is the main reason for the enhancement of the magnetic signal in the topsoil. Chemical analyses showed that the concentration of various heavy metals was higher than the mean background values for Portuguese soils, and higher in superficial soils. Heavy metals showed significant positive correlation with magnetic properties. The conclusions highlight the importance of using environmental magnetism methods and techniques in the evaluation process of soil evolution and pollution history throughout time.

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Section: Magnetic and Sem/eds Analysesmentioning

confidence: 94%

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

et al. 2014

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“…HIRM can be used as a rough guide to canted antiferromagnetic minerals in a sample (Walden and Ballantyne, 2002;Liu et al, 2007). Samples near the A1 motorway have the higher HIRM values (120.3-192.3 × 10 −3 Am −1 ), implying greater concentration of magnetically "harder" (higher coercivity) minerals (e.g.…”

Section: Resultsmentioning

confidence: 99%

“…Minerals that show a stronger resistance to magnetisation (e.g. haematite) show relatively low 100 mT acquisition ratios (referred to as "hard" (high coercivity) magnetic behaviour) (Walden and Ballantyne, 2002). Values close to Concentrations in mg kg −1 .…”

Section: Figmentioning

confidence: 99%

Relationships between magnetic parameters, chemical composition and clay minerals of topsoils near Coimbra, central Portugal

Lourenço

Rocha

Gomes

2012

Nat. Hazards Earth Syst. Sci.

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Abstract. Magnetic measurements, mineralogical and geochemical studies were carried out on surface soil samples in order to find possible relationships and to obtain environmental implications. The samples were taken over a square grid (500 × 500 m) near the city of Coimbra, in central Portugal. Mass specific magnetic susceptibility ranges between 12.50 and 710.11 × 10 −8 m 3 kg −1 and isothermal magnetic remanence at 1 tesla values range between 253 and 18 174 × 10 −3 Am −1 . Chemical analysis by atomic absorption spectrometry shows that the concentration of various toxic elements was higher than the mean background values for world soils. Higher values of susceptibility and toxic elements content were reported near roads and rivers. Urban pollution and road traffic emission seem to be the main influence for these values. A semi-quantitative X-ray diffraction study has been carried out on a representative set of subsamples, using peak areas. Illite (average 52 %), kaolinite (average 55 %), chlorite (average 6 %) and irregular illite-smectite mixed-layers (average 9 %) are the major clay minerals groups identified. Mineral composition of total fraction confirms the presence of magnetite/maghemite. The clay minerals results point to a contrast in the behavior of the main clay minerals: illite, chlorite, and kaolinite (also, smectite in some samples), which are generally in agreement with the magnetic and geochemical data. The results showed that magnetic measurements are a sensitive, fast, inexpensive and robust method, which can be advantageously applied for studying soils affected by urban and road pollution.

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“…Table 1. Mass specific mineral magnetic parameters and parameter ratios acquired during this study and an overview of their interpretation (after Walden and Ballantyne, 2002;Walden, 1999;Thompson and Oldfield, 1986). Frequency dependent susceptibility.…”

Section: Methodsmentioning

confidence: 99%

Fingerprinting of bed sediment in the Tay Estuary, Scotland: an environmental magnetism approach

Jenkins

Duck

Rowan

et al. 2002

Hydrol. Earth Syst. Sci.

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Sediment fingerprinting is commonly used for sediment provenance studies in lakes, rivers and reservoirs and on hillslopes and floodplains. This investigation explores the mixing of terrestrial and marine-derived sediment in the Tay Estuary, Scotland, using mineral magnetic attributes for fingerprinting. Samples representative of the estuary sediments and of four sources (end-members) were subjected to a suite of magnetic susceptibility and remanence measurements. Sediment samples from the beds of the Rivers Tay and Earn represented fluvial inputs while samples from the Angus and Fife coasts represented marine input. Multivariate discriminant and factor analysis showed that the sources could be separated on the basis of six magnetic parameters in a simple multivariate unmixing model to identify source contributions to estuarine bed sediments. Multi-domain magnetite signatures, characteristic of unweathered bedrock, dominate the magnetic measurements. Overall contributions of 3% from the River Earn, 17% from the River Tay, 29% from the Angus coast and 51% from the Fife coast source end-members, demonstrated the present-day regime of marine sediment derivation in the Tay Estuary. However, this conceals considerable spatial variability both along-estuary and in terms of sub-environments, with small-scale variations in sediment provenance reflecting local morphology, particularly areas of channel convergence.

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Use of environmental magnetic measurements to validate the vertical extent of ice masses at the Last Glacial Maximum

Cited by 24 publications

References 23 publications

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

Relationships between magnetic parameters, chemical composition and clay minerals of topsoils near Coimbra, central Portugal

Fingerprinting of bed sediment in the Tay Estuary, Scotland: an environmental magnetism approach

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