Recent sedimentation rates and 210Pb fluxes in Georgian Bay and Lake Huron

Abstract

The 210Pb and 137Cs profiles are determined at five locations in Georgian Bay and Lake Huron. Compaction-corrected recent sedimentation rates are derived for all locations using the 210Pb data. The rates range from 0.13 ± 0.03 mm y −1 (2.2 ± 0.4 mg cm −2 y −1) to 0.78 ± 0.06 mm y −1 (14.5 ± 1.1 mg cm −2 y −1). Except for one location, the rates show marginal to good agreement with those estimated from palynological measurements at four of the five study locations. 137Cs profiles at study locations suggest that the top portions of the sediment cores were satisfactorily retrieved during coring and sectioning operations. However, considerable downward migration of 13Cs is noted at three locations. The fluxes of excess 210Pb vary between 0.06 and 0.27 pCi cm −2 y −1. The average depositional flux is found to be considerably lower than the flux of atmospheric 210Pb. It is postulated that the deposition of atmospheric 210Pb in Lake Huron and Georgian Bay sediments is limited by the supply of scavenging particulates.