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sample must be weighed, so its remanence measurement can be normalized
by its mass. It is easiest to preweigh the sample boxes for the crushed samples
before filling the box with rock sample.
7.4
Remanence Measurements
The main point of all the study design, sample collection, and sample prep-
aration is, of course, the measurement of laboratory-applied remanences.
These measurements will monitor the variation of magnetic mineral
concentration or magnetic mineral particle size throughout the section and
these properties will hopefully encode astronomically forced climate change
that occurred during the deposition of the sedimentary rocks. The main
piece of equipment in a standard paleomagnetism laboratory for remanence
measurement is the superconducting rock magnetometer (Figure 7.5),
although less expensive, to acquire and maintain, spinner magnetometers
can also be used. Remanence measurements must follow a sequence in
which anhysteretic remanent magnetization (ARM) is measured before
any  IRMs are applied to the rock samples. IRMs applied in high fields,
≳100 mT, for example, are difficult to completely demagnetize in a standard
Figure 7.5 2G Enterprises
superconducting rock
magnetometer used for
remanence measurements.
Photograph of Lehigh
University paleomagnetism
laboratory.
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