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Measuring heterogeneous remanence in paleomagnetism
Author(s) -
Borradaile Graham J.,
Geneviciene Ieva
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl029934
Subject(s) - paleomagnetism , remanence , geology , geophysics , rock magnetism , seismology , physics , magnetization , magnetic field , quantum mechanics
Remanence directions of from the same block‐sample may be inconsistent or unrepresentative due to orientation and location heterogeneity of their remanence‐bearing minerals (RBM). Magnetization‐heterogeneity is usually undetectable at the specimen‐level but we replicated its effects by measuring 8 small specimens with stable magnetizations (8 or 5.2 cm 3 ). These were assembled into a single large multi‐specimen inside 125 cm 3 containers that were measured in a Molspin “BigSpin” magnetometer. Large‐specimen remanence directions deflect towards the direction of any strongly magnetized sub‐specimen. Differences between the large‐specimen remanence and that for the group of individually measured sub‐specimens worsened when one sub‐specimen was mis‐oriented. These discrepancies were cancelled or reduced using larger numbers of specimen orientations in the magnetometer. Conventional schemes with 4 or 6 different measurement‐orientations may fail to suppress heterogeneity‐effects whereas our 12‐orientation protocol may succeed. For most specimens, acceptable remanence‐homogeneity is present where similar remanence‐directions are recorded from 4, 6, and 12 different spin‐orientations.