EMAP_Progress_Reports_2009_2.pdf - The Heritage Council

Mayo
Bofeenaun, Co. Mayo
Early Medieval Crannog.
Grid Ref: G11290411 (111299/304116)
SMR No: MA059-011
Excavation Licence: N/A
Excavation Duration/Year: October 1992.
Site Directors: M. Keane (Irish Archaeological Wetland Unit).
The early medieval crannog at Bofeenaun, Lough More, Co. Mayo is an interesting site, being
an artificially constructed islet with enclosing wooden palisade, yet its small size, form and
on-site activities contrast with other, larger high-status sites. The crannog was located on the
east shore of a small lake in a mountainous valley below Glen Nephin, Co, Mayo, an isolated
location today which has little other archaeological evidence.
The site was first discovered and recorded by local amateur archaeologists, Michael Flynn and
Christy Lawless, and thereafter investigated by the Irish Archaeological Wetland Unit over a
two week period in October 1992. The crannog was only one of a number of archaeological
sites then exposed on the lakeshore, which included two fulachta fiadh, eighteen linear
wooden structures (interpreted as deer traps), a submerged pine forest, quarries and a
natural spring which emits iron ores. The crannog was situated on a natural knoll or
promontory of peat jutting out into the water. There was a substantial depth of peat (over
6m) under the site and it stood only 0.46m above the drained level of the lake. The crannog
was situated 29m from the dryland shoreline by a stretch of swampy ground but a possible
stone and wooden causeway may have provided access to the site. This causeway was
constructed of an irregular, linear arrangement of stakes and slabs and may have been
underwater at the time of the site’s use.
The crannog was oval in plan, measuring 14.6m by 11.8m. The edges of the site were
defined by an enclosing wooden palisade of 82 vertical posts. This palisade was gapped and
irregular and was typically constructed of a single row of roundwood oak, birch, hazel and
willow posts (typically 0.12-0.18m diam.), but there was a double row of posts facing towards
the shoreline. The palisade posts were quite short (0.65m-1m), suggesting that the palisade
merely defined or reveted the edge of the mound, not standing to any great height or serving
as a defensive feature. There may also have been a low bank of peat along the perimeter of
the site, along its southern edge. A dendrochronological date of A.D. 804 ± 9 was obtained
from a single oak timber.
The surface of the crannog was defined by a single layer of stone flags, which had been
partly washed away. The stones were densest near the palisade at the northeast side. There
was no evidence for any house or hearth. There was a small amount of bone on the site,
including cattle, horse and pig, along with some shed antler. There was some burnt bone, but
this may have been as the result of industrial activity. Finds from the surface of the crannog
included two stone mortars, a grinding stone, a hammer stone and two iron objects. The site
was covered in a large quantity of iron slag, with at least 1845 pieces identified during the
survey. Scientific analysis of a sample (74kg) of iron slag indicated that it had been produced
during primary iron production activities with such diagnostic forms as tapped slags and
furnace lining fragments. There was evidence for ore processing, the smelting and bloom
smithing of iron and the forging of objects.
There was some evidence for the spatial organisation of iron working on the site. Most of the
iron slag was concentrated in an arc, just off the peak of the knoll, at the northeast side of
the crannog, and it avoided the palisade on the south side. The furnace linings were all found
at the northern end, just to the west of the main concentration of slag or waste.
In other words, most of the iron production activity was concentrated at the north and
northeast side of the island or to the right as one entered the crannog from the causeway.
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