Sediment radioisotope dating across a stratigraphic discontinuity in a mining-impacted lake.
Application of radioisotope sediment dating models to lakes subjected to large anthropogenic sediment inputs can be problematic. As a result of copper mining activities, Torch Lake received large volumes of sediment, the characteristics of which were dramatically different from those of the native sediment. Commonly used dating models (CIC-CSR, CRS) were applied to Torch Lake, but assumptions of these methods are violated, rendering sediment geochronologies inaccurate. A modification was made to the CRS model, utilizing a distinct horizon separating mining from post-mining sediment to differentiate between two focusing regimes. (210)Pb inventories in post-mining sediment were adjusted to correspond to those in mining-era sediment, and a sediment geochronology was established and verified using independent markers in (137)Cs accumulation profiles and core X-rays.
McDonald
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Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, MI 49931, USA. cpmcdona@mtu.edu
Urban
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D005618:Fresh Water / Q000032:analysis* / Q000737:chemistry; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D008906:Mining; D008962:Models, Theoretical; D011868:Radioisotopes; D011874:Radiometry
D011868:Radioisotopes