Am 7. Oktober 2020 hält Sven Kalmring seine „Docentvorlesung“ an der Stockholmer Universität über das Thema
Between Early- and Late Birka Period.
Chronological Considerations on Birka Problems
Already under the preparation of the re-excavation in Birka’s Black Earth harbour area from 2015/16 it quickly became obvious that one of the most crucial challenges would be to find a means to date the layer sequence, characterised i.a. by a massive layer of fire-cracked stones at the seaward front of the jetty’s stone box-construction. Was it a result of some gradual accumulation or rather of one single, consciously executed event with a clear purpose? Up to then, it seemed not even the numismatic evidence could help: The re-excavation should only feature one single dirham and the numismatic spectrum from the original excavation merely was synchronised with a “hoard horizon I” (AD 780–890) and hoard horizon II (AD 890–970) – basically covering the whole of the Birka period (AD 750–975). So what to do when dendrochronology, due to the poor wooden preservation of archaeological timber, is largely inapplicable and 14C as a tool is too coarse for the specific problem at hand?
To start off, we need to ask which chronological frameworks are available for the site of Birka: Historically, the end of Birka as an urban entity was placed after Archbishops Unni’s visit in AD 936 and before Bishop Adalward’s report of a desolated town in AD 1061. The discovery of “the large silver hoard” in 1872 and its Hamdanid terminal coin led to a terminus post quem of around or after the year AD 963/967 of the Viking town. To date its beginning was less straight forward: Seeing the body of Sassānian (AD 224–651) and Umayyad coins (AD 661–750) struck before AD 750 from Birka, it was argued for it formation prior to that. A heated debate followed in which it was argued that the oriental coins featured delayed influx into the Baltic only. The study of the oval brooches from Birka, however, seemed to confirm a dating in the time during the 8th century. Thus the Birka II-publication series introduced a distinction into the early Birka period EBP (ältere Birkastufe = ÄBS) and late Birka period LBP (jüngere Birkastufe = JBS). Their somewhat reserved dating “late 8th – late 9th cent. AD” and “late 9th – 2nd half 10th cent. AD” later was provided with the absolute dates AD 750/75–860 and AD 860–975. Additionally, scholars tested dating of burial contexts via terminal coins found in 126 of the Birka-burials, yet it was found problematic due to their often unknown duration of circulation. Also, a typological approach of dating the various, yet overlapping animal styles was attempted. In the end – seeing the different Viking-age fine chronologies based on the study of various object groups for Scandinavia a such – J. Callmer’s (1977) bead chronology with nine (!) consecutive phases for a 200 years-period (AD 800–1000) seem to offer the best opportunity to date a stratigraphy by means of artefacts.
Bj. 550 – grave with coffin, Norr om Borg 2A: Bead Period BP IV (AD 875–905)
Via the study of various sets of beads– with more than nine beads as sole prerequisite – Callmer classified 122 Birka-graves to his bead periods, which can be allotted to absolute, numismatically underpinned datings. Even if the beads from Stolpe’s Black Earth-excavations in the 1870ties, too, were quantified according to typology, surprisingly the tool of bead periods (BP) was never applied on stratigraphic questions and layers representing equally “closed” find contexts. The re-excavation in the Black Earth harbour resulted in the striking amount of c. 120 beads which in fact not only allowed to date the stratigraphic sequence by means of BP:s, but – after a synchronisation with the layer sequence of the original excavation – to compare the datings gained with earlier chronological suggestions put forward.
An enhanced understanding of Callmer’s BP:s can even lead to deeper understanding of the genesis and development of Birka’s many burial grounds. The total amount of 122 bead-dated graves constitute almost exactly 10% of the excavated 1012 burials and thus can be clearly regarded as representative. Seeing this huge potential one might wonder why Callmer’s thesis did not make any larger impact earlier. This is not only due to the fact that its structure appears somewhat unwieldy, but apparently mainly because it became heavily criticised shortly after its publication: It was (erroneously) claimed that he only considered c. 66% of all possible graves with ten or more beads and thus at least some conclusions on particular bead periods/burial grounds would be insufficiently underpinned; even the cremation burials in particular would be underrepresented. Ultimately, it was stressed that the older bead periods would be largely absent in the Birka-material adduced. Having disproven the above mentioned criticism, a chronological walkthrough through the development based on BP:s shall be attempted and their actual representation for the various burial ground sections is shown. Taken the evidence of bead-dated graves as a whole, even general trends of the urban population development can be demonstrated leading to striking insights on Birka’s final phase.
As pointed out above, the application of single terminal coins for dating a burial can be challenging in regard to the antecedent coin circulation; artefact-based chronological placements of burials had shown that the average nominal difference exceeded a hundred years. Thus, the concept of a “functionally motivated [Islamic] coin stock” in opposition to the well-datable coin stock of hoards was introduced. Certainly even the problem of looped/pierced coins as pendants and an implicated likely exceeded usage must be taken into account. However, at closer sight, even some Samanid dirhams (AD 819–999) from burials appear to have an extremely short circulation which hitherto has been overlooked; particular long circulations seem mainly concern Abbasid (AD 750–1258), and to a lesser degree Umayyad (AD 661–750), issues which were never withdrawn from circulation – they already seem to have arrived as old dirhams into the Baltic after c. AD 830/40. When consequently opposing the data of all 39 bead-dated burials containing coins from Birka, in fact even delicate questions as coin circulations can be approached.
The final question, then, would be how to carry the opportunity of an approved, fine-dating via Callmer’s BP:s into future Birka-research and to finally be able to say goodbye to the coarse dichotomy of EBP and LBP only. A subsequent cluster analysis of artefact groups from bead-dated graves would allow to transfer these few datings even to hitherto undated burials, ideally containing several, individual bead-dated artefacts. The derivated datings of the latter can then be joined in multiple find combinations resulting in one specific, narrowed-down date for any respective interment. Such an undertaking for the remaining 90% (!) of the Birka-burials certainly is a mammoth task, yet indispensable not only for a closer understanding of the burial grounds and Birka as a site, but even for Viking-age artefact typologies as such.