Figure 4: Ice core records of Cu and Ag metallurgy.
From: Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago
Illimani Cu EFs (4500 BC–2000 AD) (green) and Pb EFs (4500 BC–1950 AD) (blue) exceeding in at least two consecutive data points (at least 100 years) the background (mean +2σ level of the period 4500–2000 BC) (grey) were considered to be anthropogenic Cu and Pb pollution from extensive Cu and Ag metallurgy, respectively. Pb EFs for the period 1950–2000 AD are not shown, since they represent emissions from leaded gasoline21. Periods of generalized Andean archaeological history together with dominating cultures are indicated by green shaded areas.
