Philippe, Edouard G H; St-Onge, Guillaume; Valet, Jean-Pierre; Godbout, Pierre-Marc; Egli, Ramon; Francus, Pierre; Roy, Martin: Influence of lithology on the remanent magnetization as recorded in varved sediments from the glacial Lake Ojibway (Canada) [dataset publication series]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.913372 (dataset in review)

Data results from different analysis of varved sediment from the lac Ojibway (Canada).

Natural Remanent Magnetization (NRM) of high sedimentation rate sediments provides significant information about the paleomagnetic secular variation of the Earth's magnetic field and can also potentially be used for stratigraphy. However, NRM acquisition depends on conditions inherent to the depositional environment. Besides recording a precise annual chronology, varved sediments are typically characterized by marked sedimentary changes within the same year. Since the Earth's magnetic field does not vary significantly over such short period, magnetic changes recorded by varves reflect the influence of sedimentary parameters on the recording process in the depositional record. The present study focuses on sediments from the former proglacial Lake Ojibway (~ 8.2 ka cal BP). 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.