Figure F30. Variation of remanent magnetism (RM) characteristics downhole. Note the strong magnetic material in basement and immediately above. There is evidence for a hard phase, probably hematite, at a depth of ~120 mbsf, coinciding with a hardground surface. NRM = natural remanent magnetization, ARM = anhysteretic remanent magnetization, IRM = isothermal remanent magnetization.

Figure F30. Variation of remanent magnetism (RM) characteristics downhole. Note the strong magnetic material in basement and immediately above. There is evidence for a hard phase, probably hematite, at a depth of ~120 mbsf, coinciding with a hardground surface. NRM = natural remanent magnetization, ARM = anhysteretic remanent magnetization, IRM = isothermal remanent magnetization.