Paleomagnetic inclination and latitude
For a geocentric axial dipole with normal-polarity directions expressed northward and downward, tanI=2tanλ relates field inclination to latitude.
Key knowledge
For a geocentric axial dipole with normal-polarity directions expressed northward and downward, tanI=2tanλ relates field inclination to latitude. A primary remanence suitably averaged over secular variation can therefore constrain paleolatitude after structural and polarity corrections. The axial model is invariant under longitude rotation, so such directions alone do not determine absolute paleolongitude.
Values and equations
tanI=2tanλ
- I
- normal-polarity inclination, positive downward rad
- λ
- signed paleolatitude in the axial-dipole model rad
Conditions and scope
- λ is signed geographic latitude and I signed inclination below the horizontal. Reverse-polarity directions must be transformed to the common polarity convention; polarity and hemisphere ambiguities require geological context.
- Non-dipole field components, insufficient secular-variation averaging, inclination shallowing, tilting and later magnetization can invalidate a naive latitude estimate. A magnetic direction's acquisition age can differ from the host rock's formation age.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the actual dipole-component derivation, signed inclination/latitude relation and non-GAD paragraph in the original-author web edition, with the USGS remanence explanation. Longitude nonidentifiability follows explicitly from axial rotational symmetry. Excluded old field coefficients, intensity-as-latitude inference and the source's later malformed southern-pole inequality.
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Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-paleomagnetic-latitude
- Revision
- core.1
- Structured reference record
- University core expansion