Chronology

Pb-210 age estimates were derived using the constant rate of supply (CRS) method (Appleby and Oldfield, 1978) and incorporated into Bayesian age-depth models. The prerequisite for the CRS model was not fulfilled because the flux of Pb-210 has changed through time and is not constant, but Pb-210 data are consistent with the radiocarbon ages that show sediment between 6 and 6.5 cm dates to 620 plus-minus 80 a cal BP, and 3-3.5 cm and 0-0.5 cm depth were deposited in the ''post-bomb'' (post-1950 CE) era, most likely between -40 - -44 cal yr BP (1990-1994 CE) The Cs-137 data are inconsistent with the Pb-210 CRS age model and it is possible that the steep increase in Cs-137 in the upper 2 cm relates to a Cs-137 ''soil reservoir'', which is leaching Cs-137 into the lake from snow or lake-ice melting.

Geochemistry and Sedimentology

ITRAX-XRF Raw count per second (cps) data were analysed using the Q-spec software v8.6.0 (Cox Analytical), with MSE values minimised to optimise the fit of ''as measured'' spectra to a modelled spectrum. Data are presented as percentages of the Total Scatter Normalised ratio sum (percent sigma TSN or, more simply, percent TSN, which are equivalent to percentages of the cps sum, or percent cps) to account for downcore variations in count rate, density, water and organic content. Data less than mean minus two-sigma kcps (mainly due to gaps in the core) and greater than MSE plus two-sigma (representing a poor fit between measured to modelled spectra) were filtered before analysis. ''Noisy'' elements were eliminated by comparing cps and using percent TSN thresholds of more than 0.1 percent mean and more than 0.5 percent maximum, and by examining autocorrelation profiles for each element. Elements are presented as natural log (log n or Ln) ratios.