Figure F9. Demagnetization of natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), and isothermal remanent magnetization (IRM), and of the acquisition of IRM (IRMA). The plot summarizes the magnetic characteristics of the samples. The IRM acquisition curves illustrated are consistent with the presence of magnetite. Demagnetization plots of NRM demonstrate that the samples are near the noise limit of the instrument. The ratios of ARM:IRM are indicative of larger contributions from multidomain magnetite. The high coercivity of the SIRM suggests that magnetic sulfides may be present as well.