It was 20 years ago today: Analysis of metallic residue from Early Metal Age northern Finland, with vintage dot-matrix graphs

Note: Twenty years ago today, on October 3^rd 1997, we performed analyses of metallic residue attached to ceramics from two Early Metal Age sites in Northern Finland at the Electron Microscopy Institute at Oulu University. Here are the results, along with a bit of discussion and some cell phone pictures of some sweet vintage dot-matrix graphs.

Timo Ylimaunu, Jari Okkonen, and Olli Taikina-Aho made significant contributions to this paper

Abstract

We perform qualitative Scanning Electron Microscope/Energy Dispersive Spectrometer (SEM/EDS) analysis of two metallic drops attached to ceramic from two Early Metal Age sites in northern Finland. Both had previously been visually identified as bronze. We find that one is mostly copper while the other is clearly tin bronze.

Introduction

There was much discussion in the 1990s about the chronology of metal technology in Northern Fennoscandia (Map 1), and whether, when, and to what extent it might have developed indigenously (See for example Halén 1994, Huggert 1996, Ylimaunu and Costopoulos 1998). It is in that context that we undertook the analysis of earlier finds from the early metal sites of Muhos Halosentörma (Ikaheimo 2005) and Rakanmäki (Mäkivuoti 1988). These had been visually interpreted as fragments of crucibles bearing bronze residue.

The Rakanmäki find is from a dwelling and metal production site dated between about 2000 BP and 1500 BP (Mäkivuoti 1988). The Muhos find was initially uncovered by Aarne Kopisto in 1968 and contextualized by Ikaheimo’s (2005) later excavations at the site. The occupation is radiocarbon dated at about 3500 BP, much earlier than Rakanmäki (Krapu 2003).

Map 1: Main locations discussed in the text

If both sets of remains could indeed be shown to be bronze, then the chronology of the adoption and development of metallurgy in the region (Map 1) would have to be extended. Metal finds which had previously been quite controversial and which were thought of as outliers, such as the possibly 5000 year old Polvijärvi copper ring, or the even older copper sheet from Överkalix (Halen 1994) would start to make more sense. They could be put into a timeline that contemplated the adoption of copper metallurgy in the northern Fennoscandia by about 5000 years ago, and a mature bronze industry by the time people left a broken crucible in Muhos 3500 years ago. This is not a timeline that was expected at the time for such a northern region.

Methods

The samples were detached from the material using a sterilized stainless steel surgical blade. They were analyzed qualitatively with a Jeol 733 Superprobe with SEM/EDS system attached to a Link Systems Lemas automation control.

Results

Readings for the Rakanmäki sample show nearly pure copper (Figure 1 a and b), with a very weak signal for tin. The samples for Muhos show strong signals for both copper and tin (Figure 1 b and c).

Figure 1a: Rakanmäki sample

Figure 1b: Rakanmäki sample

Figure 1c: Muhos sample

 Figure 1d: Muhos sample

Discussion

One of the samples (Figure 1d) from Muhos is definitely bronze. It is likely that the ceramic fragments are indeed from crucibles. The samples from Rakanmäki could possibly be bronze but would have to be analyzed quantitatively before anything definite can be said. It is interesting to note that it is the older of the two samples that is definitely. The presence of bronze processing technology in Muhos at 3500 BP lends credence to the idea of a deeper chronology of metallurgy in Northern Fennoscandia starting perhaps as early as 5000 BP.

References

Halén O 1994. Sedentariness during the Stone Age of Northern Sweden, Acta Archaeologica Ludensia 4.

Huggert A 1996. Early copper finds in Northern Fennoscandia, Current Swedish Archaeology 4:69-83.

Ikäheimo J 2005. Re-assessing the Bronze Age of coastal Northern Ostrobothnia – the lower Oulujoki river valley, in RJ Goldhahn (ed) Mellan sten och järn. Rapport från det 9:e nordiska bronsålderssymposiet, Göteborg 2003-10-09/12, Institutionen för arkeologi och antikens kultur, Göteborg Universitet :771-784.

 Krapu A 2003. Muhos Oulujokivarren Eteläpuoli, Tutkimuskertomus osayleiskaava-alueen arkeologisesta inventoinnista, Arkeologian Laboratorio, Oulun Yliopisto. (https://www.kyppi.fi/palveluikkuna/mjhanke/read/asp/hae_liite.aspx?id=113838&ttyyppi=pdf&kansio_id=494)

Mäkivuoti M 1988. An Iron Age dwelling site and burial mounds at Rakanmäki, near Tornio, Fennoscandia Archaeologica 5:35-45. (http://www.sarks.fi/fa/PDF/FA5_35.pdf)

Ylimaunu T and A Costopoulos 1998. Oliko kivikausi jo varhaismetallikautta? Hiidenkivi 5:18-20.