Thursday, February 6, 2014

Appendix | Dunbeg, Co. Kerry | Radiocarbon Dating

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In the main post (here) I described the Promontory Fort at Dunbeg, Co. Kerry, and the damage that has befallen it as a result of the recent storms (2013/2014), along with publishing some photographs of the site taken in 1982, by the late William Dunlop [Facebook | Website]. I would also recommend that you take a look at Colm Moriarty’s excellent recent photos on his blog: here.

View from inside clochán, through doorway, to entrance through stone rampart

Here, I want to examine the chronology of the site and the evidence from the radiocarbon dating. One thing that is clear from Barry’s (1981) publication of the excavation is that there was little in the way of direct dating evidence from finds. The finds from the site were: 13 sherds of post-Medieval pottery from the topsoil; three nails (two of iron and one of copper); a brass shirt button; a brass medal of the 'Catholic Total Abstinence League'; a possible fragment of a quern stone; a possible sandstone pestle; two small hone stones; an undecorated spindle whorl; three flint flakes with secondary working; a flint blade from a residual context; and two late 19th century clay pipe bowls. That’s it – the entire published finds list from this important excavation! Hardly the stuff of legend! The report even describes the whorl as 'Perhaps the most interesting find' (Barry 1981, 319). Of the few pieces that may actually date to the main period of occupation, none are sufficiently diagnostic to give any form of precision. It is for this reason that the four radiocarbon determinations from this site are of the highest importance.

Detailed plan of clochán at Dunbeg Promontory fort (Barry 1981)

Flint artefacts from Dunbeg (Barry 1981)

Finds from Dunbeg. 1: Brass medal;
2: spindle whorl 3: possible piece of quern stone;
4: clay pipe bowl (Barry 1981)
As mentioned in the previous post, the earliest activity on the site is related to the ditch underlying the main stone rampart. A charred hazel (corylus) base of a stake, possibly from a piece of wattle fencing, was recovered from the top of this ditch. Barry (1981, 307, 324) gives the determination as 580 b.c. ± 35, which I interpret as 2530±35 BP (UB-2216), which would result in a calibrated date of 797-539 cal BC, placing it in the latter portion of the Late Bronze Age. As noted in the main post, Kerr (et al.) (2010, 365) interpret this differently and give the determination as 2535±35 BP. It is likely that some of the recovered flint pieces relate to this phase. The remaining three dates are all within the traditional Early Christian period. The earliest of these is given by Barry (1981, 306) as 800 ad. ± 75, interpreted as being 1150±75 BP (UB-2215, 691-1018 cal AD). The determination was performed on a piece of wood charcoal recovered from the base of Fosse 1, under the rubble of a collapsed portion of the rampart. McCormick (et al.) (2011, A206) erroneously give the laboratory code for this date as UB-2219. Barry (1981, 316) gives a date of 900 ad. ± 65 from corylus charcoal from an hearth associated with the Phase 2 clochán. This is interpreted as 1050±65 BP (UB-2218, 784-1156 cal AD), though Kerr (et al.) (2010, 365) erroneously give the standard deviation as ±35. The final date from the site is given by Barry (1981, 314) as 990 ad. ± 100 from charcoal associated with the Phase 1 clochán hearth. This is interpreted as a ‘raw’ radiocarbon determination of 960±100 BP (UB-2217, 891-1263 cal AD).

 Post-excavation plan of clochán Period 1 (Barry 1981)

 Post-excavation plan of clochán Period 1 (Barry 1981)

Taken together, we can see the Early Christian phase of the site as being well under way by the 8th to 10th centuries AD, when the landward defences began to fill up. The date for the Phase 1 hearth is slightly later than the date for the Phase 2 hearth, though both are, essentially, in the period from the 9th to the mid-11th centuries. Barry (1981, 316) notes that these two dates are practically identical and sees no issue in the apparent discrepancy: “The closeness of the dates for the two phases of occupation is not surprising as both layers are fairly tenuous and are only from 18cm to 30cm apart, divided by a layer of redeposited yellow-brown clay with small stones. Therefore it seems probable that periods of occupation were of very short duration and, in any case, did not extend over more than a century. Lack of artefacts and other occupation material in either of the layers suggests that the clochán may have been occupied in periods of emergency only.”

I mourn the fact that nature has taken its course and reclaimed a portion of this beautiful site. Nonetheless, I must salute the Monuments Division of the Office of Public Works for their foresight in commissioning Terry Barry to carry out this excavation nearly 40 years ago. Barry himself is to be congratulated for producing a clear, well written, and comprehensive account of the excavations. Admittedly, samples submitted for dating today are likely to result in more accurate and precise dates, but within the limits of the technology of the time they are excellent. From a dating perspective, it may be possible that samples still survive that may be dated with the latest methods. As the excavation plan shows, almost the entirety of the area inside the stone rampart has been excavated, and is now archaeologically ‘sterile’. However, the banks and ditches were only selectively explored during the 1977 excavations. It is likely that either re-excavation of a number of these cuttings – or opening new trenches – would provide further samples suitable for radiocarbon dating. If I’m going to construct an archaeological wish list for this site, why not sample for palynology, coleoptera, and anything else that could help us to place this special place in its broadest chronological and landscape contexts?

We must not lose sight of the fact that the entirety of the site has not been lost. Any destruction to such a site is regrettable, but it is not the end of the world. We still have the opportunity to implement a sustainable engineering solution to save the remainder – or at least assess if one is possible and practical. We have been given a wakeup call – it is now up to us to ensure that it is heeded and the condition of this site (and all similarly vulnerable sites) are assessed as a matter of priority.

All calibrated dates are given at the 2σ level.

Barry T. B. 1981. ‘Archaeological Excavations at Dunbeg Promontory Fort, County Kerry, 1977Proceedings of the Royal Irish Academy 81C, 295-329.

Kerr, T., Harney, L., Kinsella, J., O'Sullivan, A. & McCormick, F. 2010 Early Medievaldwellings and settlements in Ireland. AD400-1100. Vol. 2: Gazetteer of sitedescriptions. Dublin. [Volume 1 available: here]

McCormick, F., Kerr, T., McClatchie, M. & O'Sullivan, A. 2011 The Archaeology of Livestock and Cereal Production in Early Medieval Ireland, AD 400-1100. Irish National Strategic Archaeological Research (INSTAR) programme, Dublin.

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