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U.S. Geological Survey Open-File Report 2004-1350

USGS OFR 04-1350 Figure 2.8

Figure 2.8. The zinc concentrations of individual cores compared to the 210Pb chronology. Prior to 1940 the zinc concentrations in the sound varied from 30 to 60 ppm. Concentrations increased to maximum of greater than 100 ppm in the mid 1970's and has held fairly constant from 1980 to the present.

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