The authors have declared that no competing interests exist.
Conceived and designed the experiments: FDV GLR HV. Performed the experiments: HV GLR DM NP TR AS. Analyzed the data: HV GLR DM NP TR AS FT. Contributed reagents/materials/analysis tools: HV GLR DM NP TR. Contributed to the writing of the manuscript: HV GLR DM NP TR AS FT.
Metallurgical activities have been undertaken in northern South America (NSA) for millennia. However, it is still unknown how far atmospheric emissions from these activities have been transported. Since the timing of metallurgical activities is currently estimated from scarce archaeological discoveries, the availability of reliable and continuous records to refine the timing of past metal deposition in South America is essential, as it provides an alternative to discontinuous archives, as well as evidence for global trace metal transport. We show in a peat record from Tierra del Fuego that anthropogenic metals likely have been emitted into the atmosphere and transported from NSA to southern South America (SSA) over the last 4200 yrs. These findings are supported by modern time back-trajectories from NSA to SSA. We further show that apparent anthropogenic Cu and Sb emissions predate any archaeological evidence for metallurgical activities. Lead and Sn were also emitted into the atmosphere as by-products of Inca and Spanish metallurgy, whereas local coal-gold rushes and the industrial revolution contributed to local contamination. We suggest that the onset of pre-Hispanic metallurgical activities is earlier than previously reported from archaeological records and that atmospheric emissions of metals were transported from NSA to SSA.
Population expansion and territorial colonisation increased over the course of the last 5000 years in South America. Pre-Colombian civilizations flourished first in the Northern Andes and populations progressively migrated to the South. South American animal domestication and agriculture was followed by several periods of population expansion and metallurgical activities. In particular, copper extraction and smelting started in northwestern South America as well as in Argentina around 1400 BC and spread with the various South American civilizations (Chavin, Nasca, Tiwanaku, Inca). Incas also increasingly used silver, mainly around Peru, the Titicaca basin and Potosi (Bolivia). These changes in land use as well as the extraction and processing of metals up to the present day have released detectable amounts of trace elements into the atmosphere during the second half of the Holocene (
Whereas South American metallurgy has been documented by archaeological finds, there is no record of how the resulting trace metals dispersed into the South American atmosphere through time and how far they have been transported away from production sites. To estimate the extent of anthropogenic trace metal emissions in South America, continuous and well-dated records of long-term metal deposition away from production centres are needed to highlight ancient metallurgical activities, given the absence/lack of archaeological evidence.
Our study of an ombrotrophic peat profile from Tierra del Fuego provides a continuous history of metallurgical activities in South America, and is therefore a valuable alternative to discontinuous archaeological findings. Andean trace metals of anthropogenic origin are found in our peat record from Tierra del Fuego, which suggests that they have been dispersed widely from their source areas. The data suggest for the first time that trace metals from pre-Hispanic and Hispanic Andean metallurgical activities were transported from North to South America, due to occasional North to South wind trajectories.
Continental archives, in particular raised/ombrotrophic peatlands or bogs have proven to be very useful in reconstructing past environmental changes and human activities
Upper Panel: A. Main polymetallic ores in South America (grey shaded area) and the extent of pre-Colombian civilisations and cultures discussed in the text (dark blue lines: 1-Chavin, 2-Nazca, 3-Tiwanaku; black square: 4-Ramaditas site black line: 5-Incas). B. Location of Karukinka bog in Tierra del Fuego. Lower Panel: back-trajectories for years when significant parcels of air masses travelled from NSA, specifically from the Inca, Tiwanaku and Nazca territories as well as from the Ramaditas site. Only the three most representative years are shown (see
Karukinka Park is a protected area managed by the Chilean branch of the Wildlife Conservation Society (WCS) and located at the southwestern edge of Isla Grande de Tierra del Fuego. (
Peat profiles were recovered from Karukinka bog in February 2012 using a stainless steel Russian corer of 10 cm internal diameter and 50 cm length
A clean slicing and sub-sampling procedure was applied following published guidelines
According to literature recommendations
Plant macrofossil samples (5 cm3) were boiled with 5% NaOH and sieved (mesh size 180 µm). Macrofossils were scanned using a binocular microscope (×10–×50), and identified using an extensive reference collection of type material collected during fieldwork in the study region in 2012. Plant macrofossils were assessed using the Quadrat and Leaf Count (QLC) method
The macrofossils from the 8 samples selected according to literature recommendations
Sample | Sample | Sample ID | AMS Lab ID | Age | Error | Depth |
Name | Composition | 14C BP | yr | cm | ||
KAR12-PB01/111 | GdA-2764 | NZA-51256 | 921 | 20 | 113.6 | |
KAR12/PB01B/131 | GdA-3034 | D-AMS 002878 | 1528 | 25 | 141.1 | |
KAR12/PB01B/166 | GdA-3035 | D-AMS 002879 | 1962 | 26 | 185.1 | |
KAR12/PB01/209 | GdA-2870 | NZA-52239 | 2181 | 23 | 241.5 | |
KAR12/PB01B/241 | GdA-3036 | D-AMS 002880 | 2850 | 27 | 285.2 | |
KAR12-PB01/287 | GdA-2765 | NZA-51257 | 3759 | 24 | 343.9 | |
KAR12-PB01/315 | GdA-2871 | NZA-52232 | 4482 | 26 | 380.2 | |
KAR12-PB01/363 | Unidentified graminoids | GdA-2766 | NZA-51258 | 7078 | 32 | 440.6 |
Dried samples were manually crushed using a clean agate pestle and mortar, which was rinsed between each sample using mQ water and
After proper dilution Cu, Pb and La concentrations were measured on a Quadrupole ICP-MS (Agilent Technologie 7500 ce) at the Observatoire Midi Pyrénée, Toulouse. The ICP-MS was calibrated using a synthetic multi-element standard, which was run every 8 samples, while an In-Re solution was used as an internal standard. The accuracy of the analyses was assessed by analysis of 3 international certified reference materials (SRM1947-peach leaves; SRM1515-apple leaves and GBW-07063-bush branches and leaves) and is reported in
Measured | Certified | |
6.4±1.0 | 6.6±0.8 | |
1.1±0.6 | 1.3±0.06 | |
49±1.4 | 47±3.0 | |
0.1±3.7 | 0.1±0.01 | |
3.6±0.6 | 3.7±0.4 | |
0.7±0.4 | 0.87±0,03 | |
6.3±0.8 | 5.6±0.24 | |
0.45±1.5 | 0.47±0.02 |
La results are not certified for SRM1947 and SRM1515 hence not reported. Sn has no certified values. However, the good analytical reproducibility certifies the analytical quality of Sn measurement.
After the measurements of the Pb concentration by Q-ICP-MS, mother solutions of selected samples were sub-sampled and diluted to adjust the Pb concentration to 500 mg.kg−1 prior to analyses by HR-ICP-MS at the
Based on the visual examination of the core as well as the lead isotope profile, 3 samples (237.5 cm, 34–301 yrs cal BC; 347 cm, 2354–2130 yrs cal BC; and 428 cm, 5745–5327 yrs cal BC) were processed to determine their potential volcanic origin by identifying glass shards. Dry samples were burned in a muffle furnace (550°C, 4 h) and ash residues were fine-sieved with the 10–125 µm fractions mounted in Canada Balsam on glass slides. Plane-polarised light, at ×100–400 magnification, was used to differentiate between tephra and other minerogenic material and 300 shards/grains were counted to determine their respective proportion. Fresh glass shards were identified and photographed.
The 8 radiocarbon dates as well as two eruptions from Mt. Hudson (428 cm depth, 5745–5327 yrs cal BC) and Mt. Burney (347 cm depth, 2354–2130 yrs cal BC) were used as chronological time markers with the top of the core set to year 2012 AD (when it was recovered). CLAM software
Maximum likelihood ages are expressed in years Anno Domini (AD) and Before Christ (BC). The Hudson and Burney tephras are also used as chronological markers.
Depth | Density | Calendar Age | Cu | Sn | Sb | Pb | La | 206Pb/207Pb | 2σ |
cm | (g.cm−3) | (BC/AD) | (mg kg−1) | (mg kg−1) | (mg kg−1) | (mg kg−1) | (mg kg−1) | ||
1.3 | 0.04 | 2010 | 1.59 | 0.04 | 0.02 | 0.14 | 0.14 | ||
8.7 | 0.05 | 1998 | 0.99 | 0.02 | 0.02 | 0.14 | 0.07 | ||
15.9 | 0.05 | 1985 | 0.84 | 0.03 | 0.02 | 0.28 | 0.25 | 1.181 | 0.001 |
22.1 | 0.05 | 1972 | 0.84 | 0.02 | 0.02 | 0.27 | 0.08 | ||
28.0 | 0.10 | 1957 | 0.55 | 0.04 | 0.01 | 0.31 | 0.08 | ||
30.8 | 0.14 | 1949 | 0.84 | 0.02 | 0.01 | 0.48 | 0.55 | 1.182 | 0.003 |
34.8 | 0.19 | 1936 | 0.89 | 0.02 | 0.01 | 0.20 | 0.20 | 1.179 | 0.0001 |
36.0 | 0.15 | 1932 | 0.40 | 0.03 | 0.01 | 0.21 | 0.07 | ||
42.0 | 0.15 | 1910 | 0.46 | 0.01 | 0.01 | 0.19 | 0.06 | ||
50.4 | 0.07 | 1874 | 0.85 | 0.01 | 0.01 | 0.12 | 0.15 | 1.195 | 0.0003 |
54.3 | 0.14 | 1853 | 1.14 | 0.06 | 0.02 | 0.23 | 0.30 | ||
58.0 | 0.10 | 1831 | 0.81 | 0.01 | 0.01 | 0.15 | 0.15 | 1.185 | 0.004 |
62.0 | 0.09 | 1805 | 1.20 | 0.02 | 0.01 | 0.17 | 0.16 | ||
66.0 | 0.06 | 1776 | 1.91 | 0.01 | 0.01 | 0.11 | 0.11 | ||
72.6 | 0.06 | 1722 | 0.69 | 0.13 | 0.04 | 0.10 | 0.10 | 1.191 | 0.001 |
79.9 | 0.08 | 1653 | 0.99 | 0.01 | 0.01 | 0.15 | 0.20 | 1.193 | 0.001 |
84.1 | 0.09 | 1607 | 1.39 | 0.03 | 0.01 | 0.16 | 0.20 | 1.188 | 0.003 |
92.1 | 0.08 | 1509 | 2.24 | 0.02 | 0.01 | 0.17 | 0.33 | 1.190 | 0.002 |
96.1 | 0.10 | 1454 | 2.38 | 0.02 | 0.01 | 0.13 | 0.46 | 1.198 | 0.004 |
102.7 | 0.06 | 1355 | 2.12 | 0.03 | 0.02 | 0.14 | 0.63 | ||
109.2 | 0.07 | 1244 | 2.48 | 0.03 | 0.02 | 0.22 | 0.63 | ||
117.1 | 0.05 | 1093 | 3.63 | 0.02 | 0.02 | 0.12 | 0.54 | ||
122.2 | 0.08 | 988 | 4.56 | 0.07 | 0.02 | 0.20 | 0.87 | 1.194 | 0.002 |
127.7 | 0.09 | 871 | 3.43 | 0.05 | 0.02 | 0.19 | 0.64 | ||
135.3 | 0.09 | 713 | 4.03 | 0.08 | 0.05 | 0.19 | 1.14 | ||
142.7 | 0.08 | 571 | 3.62 | 0.04 | 0.01 | 0.37 | 3.13 | 1.193 | 0.001 |
146.9 | 0.11 | 499 | 6.71 | 0.06 | 0.02 | 0.85 | 7.30 | 1.197 | 0.0002 |
158.0 | 0.13 | 339 | 15.28 | 0.15 | 0.07 | 1.59 | 15.19 | 1.198 | 0.001 |
161.8 | 0.12 | 293 | 21.53 | 0.11 | 0.10 | 2.00 | 14.76 | ||
164.4 | 0.11 | 264 | 21.55 | 0.15 | 0.12 | 1.90 | 14.72 | ||
168.0 | 0.10 | 228 | 17.10 | 0.12 | 0.08 | 1.56 | 11.37 | ||
171.8 | 0.11 | 194 | 24.03 | 0.13 | 0.08 | 1.36 | 10.32 | 1.197 | 0.002 |
175.4 | 0.08 | 165 | 22.19 | 0.06 | 0.07 | 1.28 | 9.35 | ||
179.0 | 0.07 | 140 | 24.72 | 0.05 | 0.08 | 1.23 | 7.62 | ||
182.8 | 0.09 | 117 | 10.69 | 0.07 | 0.06 | 0.80 | 6.26 | ||
190.0 | 0.08 | 83 | 18.05 | 0.05 | 0.06 | 0.91 | 5.37 | ||
195.4 | 0.07 | 64 | 14.49 | 0.05 | 0.05 | 0.93 | 5.73 | 1.190 | 0.001 |
201.3 | 0.06 | 46 | 12.46 | 0.05 | 0.07 | 0.68 | 4.81 | ||
207.8 | 0.08 | 29 | 12.91 | 0.05 | 0.05 | 0.87 | 6.66 | ||
215.2 | 0.07 | 6 | 9.1 | 0.1 | 0.1 | 1.4 | 5.4 | ||
221.9 | 0.08 | −21 | 13.86 | 0.07 | 0.04 | 1.39 | 6.85 | ||
227.4 | 0.06 | −50 | 21.63 | 0.26 | 0.07 | 1.63 | 7.68 | ||
231.5 | 0.06 | −77 | 20.04 | 0.09 | 0.06 | 1.33 | 6.21 | 1.196 | 0.002 |
237.5 | 0.16 | −128 | 24.53 | 0.09 | 0.06 | 1.50 | 9.00 | 1.198 | 0.003 |
244.3 | 0.13 | −204 | 4.49 | 0.04 | 0.03 | 0.44 | 5.64 | ||
250.2 | 0.09 | −285 | 9.26 | 0.04 | 0.04 | 0.80 | 6.35 | ||
253.1 | 0.14 | −330 | 4.68 | 0.03 | 0.03 | 0.40 | 4.78 | 1.199 | 0.001 |
258.7 | 0.12 | −424 | 5.30 | 0.04 | 0.03 | 0.41 | 4.36 | ||
264.8 | 0.10 | −535 | 5.19 | 0.03 | 0.03 | 0.33 | 2.96 | ||
270.2 | 0.10 | −639 | 5.78 | 0.05 | 0.03 | 0.41 | 3.79 | 1.196 | 0.001 |
274.0 | 0.09 | −714 | 5.64 | 0.04 | 0.03 | 0.39 | 3.98 | ||
279.7 | 0.10 | −828 | 3.0 | 0.1 | 0.0 | 0.4 | 2.9 | ||
285.2 | 0.09 | −937 | 2.35 | 0.02 | 0.02 | 0.32 | 2.03 | 1.198 | 0.001 |
289.3 | 0.09 | −1017 | 2.52 | 0.03 | 0.02 | 0.31 | 1.82 | ||
293.4 | 0.14 | −1096 | 3.49 | 0.08 | 0.04 | 0.25 | 2.04 | ||
300.9 | 0.10 | −1239 | 5.88 | 0.03 | 0.04 | 0.41 | 2.15 | 1.196 | 0.003 |
304.9 | 0.09 | −1316 | 6.28 | 0.04 | 0.03 | 0.21 | 1.41 | ||
308.6 | 0.08 | −1387 | 4.44 | 0.02 | 0.02 | 0.26 | 1.45 | ||
312.2 | 0.13 | −1457 | 4.63 | 0.07 | 0.06 | 0.58 | 2.87 | 1.195 | 0.002 |
320.5 | 0.10 | −1623 | 6.46 | 0.04 | 0.04 | 0.27 | 1.38 | ||
325.6 | 0.13 | −1729 | 9.90 | 0.07 | 0.06 | 0.54 | 2.47 | ||
330.8 | 0.11 | −1842 | 6.31 | 0.06 | 0.04 | 0.54 | 2.78 | 1.199 | 0.002 |
334.8 | 0.12 | −1932 | 6.25 | 0.06 | 0.05 | 0.68 | 3.29 | ||
339.8 | 0.12 | −2050 | 6.60 | 0.04 | 0.05 | 0.48 | 2.79 | ||
343.9 | 0.12 | −2152 | 6.62 | 0.09 | 0.04 | 0.85 | 3.56 |
Sample depths and maximum likelihood calendar ages (positive values are ages Anno Domini, negative values are ages Before Christ) are also reported.
The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model
Note that all trajectories are counted once in the source location grid cell and once per intersecting grid cell.
Out of the 64 years investigated in this model (from 1948 to 2012,
The year 1968 is given as a comparison to show a year where no air back trajectory is coming from NSA (see
Karukinka bog is located on a small hill beside the main Karukinka Valley. It consists of an open area where the surface vegetation is dominated by
Mineral grains are from the Hudson and Burney tephras (red lines).
Of the 3 samples submitted for petrographic analysis, tephra horizons were identifiable in two (347 cm depth, 2354–2130 yrs cal BC and 428 cm depth, 5745–5327 yrs cal BC). The remaining sample contained small numbers of tephra shards but did not exceed baseline levels, which are typically present in such close proximity to numerous volcanic sources.
The tephrochronology of SSA is relatively well known
Copper and Sb concentrations remain below 7 mg.kg−1 from the base of the core to approximately 250 cm depth (
Lead isotopes fluctuate within a range typical for the Upper Continental Crust (1.18<206Pb/207Pb <1.21) with three slight shifts towards more radiogenic values around 425 cm, 351 cm and 195 cm depth. In shallower samples (above 60 cm depth), the 206Pb/207Pb shifts towards more radiogenic values, which are typical for a mix between anthropogenic and natural sources.
Whereas metallurgical activities occurred throughout South America since ca 2000 BC, there is no evidence that pre-Hispanic metal objects or artifacts reached Tierra del Fuego
The upper part of the Karukinka peat bog (4200 years) is ombrotrophic as demonstrated by the plant macrofossil succession (see
Maximum likelihood ages are expressed in years Anno Domini (AD) and Before Christ (BC). The age scale is cut at 1750 AD and the Sb/LaUCC scale changes at 1750AD. 1. Onset of Cu metallurgy, 2. Chavin, 3. Nazca and Ramaditas, 4. Tiwanaku, 5. Inca (transition from Cu to Ag mining), 6. European Colonization, 7. Gold rush and bronze industry, 8. Leaded gasoline period, 9. Unleaded gasoline period (see text for details).
The lower part of the peat profile (6500 BC to 2200 BC) is not ombrotrophic and may have been exposed to local in-washed mineral inputs and changes in redox conditions. As we want to investigate atmospheric metal deposition, we therefore do not interpret this part of the profile in detail but focus our interpretations on the ombrotrophic part of the sequence (2200 BC to present day).
The oldest archaeological evidence for copper metallurgy dates back to ca. 1400 BC in Southern Peru and the following centuries saw its development mainly in the Bolivian Altiplano, Northern Chile but also in the Antofagasta and northeast Argentina regions. This is based on archaeological evidence for metal ore extraction and smelting, various ritual objects, artifacts and weapons
Civilizations such as the Chavin and Nazca are mainly known to have worked textiles and ceramics but they also processed copper
Copper production intensified under the control of the Incas (1480–1532 AD)
Although the most recent section of the Karukinka core is not as well chronologically constrained as the pre-Hispanic section, we can identify excursions in the metals/LaUCC ratios and Pb isotopic profiles, which match historical data from the 18th to 20th century. We therefore present a tentative interpretation for this section of the profile. The early 18th century sees a depletion in Ag resources and a transition to Sn mining in the Potosi area
The Karukinka peat bog sequence records past metallurgical activities in South America, as the area was isolated from any local anthropogenic sources until the 19th century. Based upon the excellent agreement between variations in UCC-normalized Cu, Pb, Sb and Sn to La ratios, modern-time back-trajectories and historical data, we conclude that Cu metallurgy predates archaeological evidence and that NSA atmospheric emissions from pre-Hispanic civilizations through to the Industrial Revolution are recorded in SSA.
Back trajectory frequency corresponding over Tierra del Fuego 1948 to 2012.
(PDF)
This research is supported by a Young Researcher Grant of the