Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago

Abstract

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200-800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700-50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures.

Figure 1. Location of the Illimani and sites mentioned in the text together with the earliest cultures in South America.

Left: Map of South America (Credit Uwe Dedering, CC BY-SA 3.0, http://creativecommons.org/licenses/by-sa/3.0 or GFDL, http://www.gnu.org/copyleft/fdl.html, via Wikimedia Commons (2010) without changes, Date of access: 31/05/2016) with the Illimani (red star), the inset shows the frequency plot of 5-day back trajectories for the Zongo valley close to the Illimani for the period 1989–1998 using HYSPLIT and the NCEP/NCAR reanalysis. Back trajectories were run every 6 hours. Right: The schematic extension of the earliest cultures in South America around 500 BC, 300 AD, and 800 AD.

Figure 2. Ice core records of Cu, Pb, Sb, and Ce concentrations together with EFs, and lake levels of the Lake Titicaca for the period 4500 BC–2000 AD.

Concentrations (bars) and EFs (black lines) are shown as 50-year medians. Pb data for the period 0–2000 AD are from ref. . Reconstructed lake levels of the Lake Titicaca are additionally presented in black and grey (inverse scale).

Figure 3. Illimani Cu EFs compared to Cu records from other natural archives in South America.

Illimani Cu EF record (green, 50-year medians) together with Quelccaya ice core Cu EFs (grey, 50-yr medians), sediment core anthropogenic Cu from Laguna Pirhuacocha (blue, non-equidistant data), and peat bog Cu/La ratios from Tierra del Fuego (brown, non-equidistant data). Periods of generalized Andean archaeological history together with dominating cultures are indicated by green shaded areas.

Figure 4. Ice core records of Cu and Ag metallurgy.

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 gasoline. Periods of generalized Andean archaeological history together with dominating cultures are indicated by green shaded areas.

Figure 5. Cu artefacts documenting Cu metallurgy during periods with enhanced anthropogenic Cu emissions.

From the left: (1) Chiripa Cu pin, bent, excavated by W. Bennett in 1934 at the Chiripa House 2 site (CH-H213), occupied during the late Chiripa period (~600–100 BC) (Courtesy of the Division of Anthropology, American Museum of Natural History, #41.1/3895); (2) Moche belt ornament (Peru, 2^nd–7^th century), Credit: The Metropolitan Museum of Art, www.metmuseum.org, bequest of Jane Costello Goldberg, from the Collection of Arnold I. Goldberg, 1986; (3) I shaped architectural cramp from the Puma Punka pyramid at Tiwanaku, Bolivia, composed of Cu-As-Ni bronze alloy; (4) Inca tumi (ceremonial knife) made of tin bronze (Peru, 15^th- early 16^th century), Credit: The Metropolitan Museum of Art, www.metmuseum.org, bequest of Jane Costello Goldberg, from the Collection of Arnold I. Goldberg, 1986, (5) Large bronze signal cannon, Spanish Colonial, 1600 s, Peru; Credit: Daniel Frank Sedwick, LLC, www.sedwickcoins.com; (6) modern Cu wires (Image: Anja Eichler).

Figure 6. Ice core records of Cu EFs and Cu ore production in South America.

Illimani Cu EFs (10 year means, green) and annual Cu ore production in South America (grey) are shown.