Chronology of Elk Lake sediments: Coring, sampling, and time-series construction
Published:January 01, 1993
Roger Y. Anderson, J. Platt Bradbury, Walter E. Dean, Minze Stuiver, 1993. "Chronology of Elk Lake sediments: Coring, sampling, and time-series construction", Elk Lake, Minnesota: Evidence for Rapid Climate Change in the North-Central United States, J. Piatt Bradbury, Walter E. Dean
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A 22 m series of cores from a continuously laminated sequence of postglacial sediment was recovered from 29.6 m of water from the deepest part of Elk Lake, Clearwater County, Minnesota, by piston and freeze-coring methods during the winters of 1978 and 1982. A varve time series constructed and used as a basis for subsampling the cores and samples, based on the varve chronology, allows precise determination of fluxes of geochemical and biological sediment components. Chronological and petrographic studies have shown that the laminations are varves and their measurement and enumeration has produced a 10,400 year time series that estimates the rates and timing of paleolimnologic and paleoenvironmental changes in Elk Lake and its drainage. A radiocarbon date from surface sediment is 850 years. The difference between radiocarbon and varve dates continues down core; varve dates are older than radiocarbon dates, probably because of systematic incorporation of dead carbon (as bicarbonate) in organic matter in the sediment. Varve-dated boundaries of pollen zones in the Elk Lake cores compare closely with the ages of the same zones in cores from nearby lakes that have been radiocarbon dated.