Magnetic Parameter Analysis in Studies of Holiday Beach, Western Lake Erie, Ontario, Canada

Magnetic measurements offer advantages such as low costs, speed, sensitivity and flexibility over other techniques in studying a wide range of environmental processes. Many beaches of Lake Erie (42°N, 81°W) in Canada contain highly magnetic sands. In this work, we utilize magnetic susceptibility (LF), isothermal remanent magnetization (IRM) acquisition curves, partial anhysteretic remanent magnetization (pARM) spectra and hysteresis measurements to investigate five profiles at Holiday Beach on the northern shoreline of western Lake Erie. A contour plot of the LF values for the 5 profiles shows a high concentration of magnetic minerals near to, but not right at the water's edge, and lower concentrations at the water's edge and in the inland area, close to vegetation. This occurs in three profiles (3, 4 and 5, with the highest LF value (4.3×10-3 SI) in profile 5. Profiles 1 and 2 are relatively flat with low LF (< 5×10-4 SI) values throughout, similar to the background values in the other three profiles. A distinctive magnetite component,with low coercivity and of PSD-MD size, is present in the beach sand, and produces the aomalies mentioned previously. pARM spectra for profiles 3, 4, and 5 show a peak at 8-15 mT, indicating lower coercivity and a PSD to MD magnetic size. In contrast, such features are not distinct in the latter two profiles. The variation of pARM is consistent with the LF distribution, suggesting coarser magnetic minerals contribute to the strong magnetic susceptibility LF anomalies. The average Bloemendal S-300 ratio of all samples is close to 1 (-0.96), indicating the dominant magnetic mineral of the beach sand has low coercivity. The difference between S-300 and S-100 ratio is lower than 0.1, suggesting that little fine- grained material is present in these samples. However, this difference is >0.1 at the water's edge in profile 1 and close to the inland area in profile 4, suggesting that some finer grains probably occur in the sand. Hysteresis coercivity (Bc) is low and generally decreases from water edge to inland area, and remanent coercivity Bcr is generally consistent, so the ratio Bcr/Bc increases. The results suggest that magnetic parameters may be used to understand shoreline processes.