Techniques for combining geochemical data from a till survey (2438 samples) and a lake sediment survey (17 447 samples) are assessed to determine a rigorous method for comparing the two sampling media. This study is based on five elements, (Cu, Ni, Fe, Pb and Zn) from overlapping geochemical surveys in Labrador, Canada. Two methods for comparing the till and lake sediment geochemical data are: (1) gridding and (2) nearest neighbour. Pearson correlation coefficients between media are low (<0.2) for Cu, Fe and Zn and only Ni has a correlation significant at the 95% confidence level (r2 = 0.45). Results from gridding show slightly higher correlations. Differences are most evident at the extremes, as anomalously high element concentrations in one medium typically do not correlate with high values in the other medium. Correlations between media increase as distance decreases for Ni, Pb and Zn; however, no such trend is evident for Cu or Fe. The nearest neighbour method has several advantages: this procedure retains the original data and it permits calculation of statistics such as distance and direction between the points. The differences between the geochemical results from the two media highlight the synergistic value of multi-media geochemical sampling.

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