Influence of lithology on the remanent magnetization as recorded in varved sediments from the glacial Lake Ojibway (Canada)

It concentrates on a sequence of centimetre-thick summer and winter beds that were sampled individually. Paleomagnetic, granulometric and geochemical analyses were conducted on each individual layer. A mean inclination shallowing of 13° is observed in winter beds, while summer beds are not systematically affected by shallowing.

Magnetic declinations follow, on average, the expected field direction, but differences of up to 20° occur between successive beds. Summer beds are thicker than winter beds and characterized by stronger magnetic susceptibility, higher Ca/Fe ratios and coarser sedimentary and magnetic grains. This grain size pattern reflects the input of coarser detrital particles during summer, while the finer fraction remained in suspension until deposition in winter.

Differential compaction of the winter and summer beds and the physical properties of sediment. These results indicate that lithological changes can play a dominant role on magnetic records of sediments.