High-resolution magnetic analysis of sediment cores; strengths, limitations and strategies for maximizing the value of long core magnetic data

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doi: 10.1016/j.pepi.2005.03.021
Author(s): Roberts, Andrew P.
Author Affiliation(s): Primary:
University of Southampton, National Oceanographgy Centre, Southampton, United Kingdom
Other:
University of California at Davis, United States
Florida International University, United States
University of Hawaii at Manoa, United States
Volume Title: ODP contributions to paleomagnetism
Volume Author(s): Sager, William W., editor; Acton, Gary D.; Clement, Bradford M.; Fuller, Michael
Source: ODP contributions to paleomagnetism, edited by William W. Sager, Gary D. Acton, Bradford M. Clement and Michael Fuller. Physics of the Earth and Planetary Interiors, 156(3-4), p.162-178. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-9201 CODEN: PEPIAM
Note: In English. 51 refs.; illus., incl. 1 plate
Summary: Narrow-access long-core cryogenic magnetometers enable measurement of a range of magnetic parameters at a speed and resolution that cannot be matched by other techniques. Despite the revolutionary impact that these instruments have had on paleomagnetic and environmental magnetic investigations, some fundamental constraints limit their usefulness. First, the pick-up coils have different response functions for the transverse and axial measurement axes. Transverse coils typically have regions of negative response on either side of the main response peak, whereas the axial coil usually lacks the negative response lobes. Zones of negative response affect the measured remanence intensity, for which corrections can be made by normalizing the measured magnetic moment by the area under each respective response curve. This correction works adequately for homogeneously magnetized cores. Second, in cores with significant changes in remanence intensity, the ratio of axial to transverse moment varies with intensity change, which can introduce spurious artefacts into the paleomagnetic directional record. Deconvolution is required to remove such effects. Third, measurements of non-centred samples with irregular cross-section (e.g., split core measurements), cause geometric effects that can introduce small but paleomagnetically important artefacts. Corrections for such effects are only possible if spatial variability of the magnetometer response is known throughout the entire measurement volume rather than solely along the centre-line of the magnetometer. Fourth, analysis of cores deposited at rates >10 cm/ky is desirable to minimize the effects of measurement smoothing. Finally, measurements of magnetic susceptibility should be conducted using loop sensors with a similar response function as a u-channel magnetometer to ensure comparability of data. Routine adoption of these five strategies should help to maximize the value of long-core magnetic measurements. Abstract Copyright (2006) Elsevier, B.V.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Anhysteretic remanent magnetization; Calibration; Cores; Corrections; Deconvolution; Demagnetization; Geophysical methods; High-resolution methods; Instruments; Magnetic field; Magnetic intensity; Magnetic methods; Magnetic properties; Magnetic susceptibility; Magnetization; Magnetometers; Marine sediments; Measurement; Ocean Drilling Program; Paleomagnetism; Remanent magnetization; Sediments
Record ID: 2007053205
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

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