Table 2.
Explanation of magnetic parameters used to characterise down-core changes in the geomagnetic record of the urban pond sediments24–26.
| Parameter | Interpretation |
|---|---|
| Low frequency susceptibility (χLF) | Ferrimagnetic concentration. Low values may indicate the presence of paramagnetic minerals. The signal may be dominated by antiferromagnetic content if the sample has little or no ferrimagnetic component |
| Susceptibility frequency dependence (χFD%) | High χFD% reveals a superparamagnetic (SP) component and low χFD% indicates a lack of SP grains |
| Anhysteretic remanence magnetisation (ARM) and susceptibility of ARM (χARM) | Sensitive to concentrations of fine-grained magnetic particles, particularly those of the stable single domain (SSD) grain size (0.03–0.5 µm) |
| Saturated isothermal remanence magnetisation (SIRM) | Reflects the concentration of all remanence-carrying minerals. SIRM is also sensitive to magnetic grain size and reflects the magnetic mineral assemblage |
| SOFT−20mT IRM | Indicative of ‘soft’/multi domain (MD) ferrimagnetic grains |
| HIRM | Indicative of ‘hard’/antiferromagnetic content |
| S-RATIO | Indicative of soft and hard mineral contributions. S-RATIO values ~ < − 0.7 are ‘soft’ magnetic grains; > − 0.3: dominating antiferromagnetic component. Intermediate values ~ -0.4 to ~ 0.6: dominant SD ferrimagnetic signal with potential mix of antiferromagnetic grains |
| SIRM/χLF | Low ratios: paramagnetic minerals; high ratios: canted-antiferromagnetic minerals. For samples with similar mineralogy, SIRM/χLF can also be used to assess grain size variations. High values: SSD grains; low values: SP/MD grains |
| χARM/SIRM | Discriminates variations in magnetic grain size. High ratios: SSD ferrimagnetic grains; low values: coarser (MD) grains |
| SIRM/ARM | Indicative of magnetic grain size variations in samples dominated by ferrimagnetic minerals. Low ratios: SSD grains; high ratios: MD grains |