Palaeomagnetism and magnetic fabric of recent sediments from the Severn estuary system
Palaeomagnetism and magnetic fabric of recent sediments from the Severn estuary system
The palaeomagnetism and magnetic fabric of unconsolidated recent sediments from eight Severn Estuary cores and one Irish Sea core have been investigated. Most specimens displayed high remanence stability and a stable characteristic component of magnetisation was isolated during progressive a.f. demagnetisation. All cores reveal palaeomagnetic inclination errors of variable magnitude which can be grouped into two types. This grouping has been used to identify the presence of two major types of sediment deposition processes within the Severn Estuary. Curie point determinations, XRD analyses of magnetic mineral separates and IRM acquisition curve analyses confirm that single domain titanomagnetite is the principal carrier of the magnetic remanence. The primary magnetic fabric identified for these cores is characteristic of sediments deposited in the presence of strong bottom currents. Four cores display lineations which are parallel to the channel axis and five cores display lineations which are oblique to this axis. From the orientation of the Kmax axes, a sediment circulation pattern which envisages a south-easterly drift of fine materials in Bridgwater Bay and a north-westerly drift in the Newport Deep area, as well as shoreward transport in both areas has been proposed. The presence of a high redox potential identified from the downcore behaviour of the NRM intensity and susceptibility values of specimens from cores BC263, BC264 and BC266 has been confirmed by the result of IRM and geochemical analyses. These results have been used to confirm the existence of two major types of sediment deposition processes within the Estuary. Sewage and industrial inputs into the estuary enhance the carbon content of the estuarine sediments and may have contributed significantly to the onset of the high redox potential in some parts of the study area. Results of remanence anisotropy measurements carried out on thirteen specimens from core BC264 show good agreement with those of susceptibility analyses and suggest that a combination of both these methods should provide additional information concerning the domain-state of the magnetic minerals.
University of Southampton
1988
Imienwanrin, Augustine
(1988)
Palaeomagnetism and magnetic fabric of recent sediments from the Severn estuary system.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The palaeomagnetism and magnetic fabric of unconsolidated recent sediments from eight Severn Estuary cores and one Irish Sea core have been investigated. Most specimens displayed high remanence stability and a stable characteristic component of magnetisation was isolated during progressive a.f. demagnetisation. All cores reveal palaeomagnetic inclination errors of variable magnitude which can be grouped into two types. This grouping has been used to identify the presence of two major types of sediment deposition processes within the Severn Estuary. Curie point determinations, XRD analyses of magnetic mineral separates and IRM acquisition curve analyses confirm that single domain titanomagnetite is the principal carrier of the magnetic remanence. The primary magnetic fabric identified for these cores is characteristic of sediments deposited in the presence of strong bottom currents. Four cores display lineations which are parallel to the channel axis and five cores display lineations which are oblique to this axis. From the orientation of the Kmax axes, a sediment circulation pattern which envisages a south-easterly drift of fine materials in Bridgwater Bay and a north-westerly drift in the Newport Deep area, as well as shoreward transport in both areas has been proposed. The presence of a high redox potential identified from the downcore behaviour of the NRM intensity and susceptibility values of specimens from cores BC263, BC264 and BC266 has been confirmed by the result of IRM and geochemical analyses. These results have been used to confirm the existence of two major types of sediment deposition processes within the Estuary. Sewage and industrial inputs into the estuary enhance the carbon content of the estuarine sediments and may have contributed significantly to the onset of the high redox potential in some parts of the study area. Results of remanence anisotropy measurements carried out on thirteen specimens from core BC264 show good agreement with those of susceptibility analyses and suggest that a combination of both these methods should provide additional information concerning the domain-state of the magnetic minerals.
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Published date: 1988
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Local EPrints ID: 461097
URI: http://eprints.soton.ac.uk/id/eprint/461097
PURE UUID: eebb3d1b-87ff-4a99-b202-6a0c60832d3d
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Date deposited: 04 Jul 2022 18:35
Last modified: 04 Jul 2022 18:35
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Author:
Augustine Imienwanrin
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