REY geochemistry of freshwater ferromanganese concretions
Joyceline Lo, Dr. Tom Al
Department of Earth and Environmental Sciences, University of Ottawa
Joyceline Lo, Dr. Tom Al
Department of Earth and Environmental Sciences, University of Ottawa
The shallow post-glacial lacustrine system of Magaguadavic Lake, New Brunswick, Canada, houses freshwater ferromanganese concretions (Fe-Mn concretions) that sequester elements from the surrounding lake water. In this study, rare earth elements and yttrium (REY) incorporated in Fe-Mn concretions were used to obtain a more comprehensive view of the Holocene climate and the paleoecological conditions of the catchment area. Electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) methods were used to analyze the concretions. From the data obtained, the inverse correlation of Fe and Mn was a result of Fe(II)- and Mn(II)-rich groundwater flux fluctuations and the availability of dissolved oxygen in the water column. Additionally, negative Ce anomalies correlate with higher Mn concentrations in the system. This negative correlation was attributed to high amounts of siderophores and organic fluxes in the lake that had originated from the surrounding forested area. From the results of this study, vegetation and productivity continued to evolve and mature following the Wisconsin glaciation 15,000 years ago. Our results provide experimental evidence for the development of negative Ce anomalies as productivity and organic fluxes continued to increase in the catchment area.