A unified stable Pb sediment chronology for Halifax, Nova Scotia, Canada


Establishing chronologies for lake sediment cores is essential to determine causal relationships that form the basis of many paleolimnological investigations. ^210^Pb dating is an essential tool to establish recent (<150 years) lake sediment chronologies, however there are cases in which ^210^Pb chronologies are difficult to obtain due to low concentrations of ^210^Pb, difficult to interpret due to complicated ^210^Pb accumulation history, or not feasible to measure due to time, cost, or availability constraints. Stable Pb is present in measurable concentrations in many lake sediments, is easily and cost-effectively measured, and often follows a regional pattern of increase following aerial deposition of particulates from industrial development. We measured stable Pb concentrations in seven ^210^Pb-dated sediment cores near Halifax, Nova Scotia using X-Ray Fluorescence Spectroscopy. Pb concentrations ranged from non-detect (~2 ppm) to 155 ppm, with a substantial increase observed between 1900 and 1930. Peak lead concentration dates were variable, but generally ocurred between 1970 and 1990. The timing of the initial increase was within the range of ^210^Pb age-depth model error for all lakes, suggesting a common aerial source for lead in the Halifax region. Using stable Pb concentrations, ^210^Pb age-depth model error, and rescaling methods, a unified stable Pb sediment chronology was constructed for the Halifax region. This chronology could be applied to create age-depth models for lake sediment cores for which no ^210^Pb data are available.

Ontario-Québec Paleolimnology Symposium
Dewey Dunnington
Geoscientist, Programmer, Educator