Paleomagnetic and rock magnetic techniques provide means of understanding
the Earth's ancient geomagnetic field by using the magnetic record contained
in rocks and archeological materials. Most materials contain a record of
the direction of the magnetic field that was present at the time the rock
was formed. Variations in field intensity also can be obtained from those
rocks and archeological materials that cooled fromhigh temperature in the
Earth's field. The knowledge gained is then applied toward the solution
of geologic problems. The magnetic polarity record of the past few million
years can provide the means of dating young geologic materials where isotopic
determinations are unavailable or equivocal. Magnetic directions are used
to detect tectonic disruptions ranging from tilt and rotation of small
structural blocks to large-scale movements of terranes and continental
masses. Magnetic directions also are usedto differentiate between lava
flows or archeological artifacts with a resolution that is unattainable
with radiometric dating. Knowledge of variations in geomagnetic field strength
during Quaternary time is important for determining the production rate
of cosmogenic nuclides that are used in dating and correlation of geologic
materials.
