2007:1580 - Ballycahill, Tipperary

The N7 Nenagh to Limerick high-quality dual carriageway project is being developed by Limerick County Council in conjunction with North Tipperary County Council and the National Roads Authority.
Preliminary test-trenching of the site was carried out by the Archaeological Services Unit in mid-June 2006 (A026/003) and identified eight possible pits and a large stone spread. The stone feature was thought not to be natural in origin by consultant geologist Antony Beese.
Excavation took place between 25 September 2006 and 5 January 2007. The site lay on a very gentle westward incline situated in low-lying boggy terrain dominated by rough grazing. A total area of 7256m2 of topsoil was mechanically stripped from the area. The area to be excavated was defined by the CPO limit to the north, and by the access track at the toe of the N7 embankment to the south. As the excavation progressed it became clear that the stone spread continued westwards and approval was granted for further testing and stripping west of the exposed portion.
The eight pits identified in testing were investigated and proved to be non-archaeological.
The site’s stratigraphy is crucial to its interpretation. The platform was constructed on Holocene sediments composed of white calcareous marl with abundant freshwater snail shells. A number of Giant Irish Deer (Megaloceros giganteus) bone fragments were recovered from the marl surface. Above the marl bed, a brown organic mud, also mollusc-rich, accumulated. The above-mentioned layers were laminated in regular bands on a horizontal plane. Significantly, large limestone boulders had clearly displaced the underlying soft sediments. The lake chalk was squeezed laterally, with only a thin lens trapped beneath the boulders’ bulk. The cavity created by this disturbance was filled with a highly mixed calcareous organic mud. This produced a characteristic light-brown orb which was subsequently shown to surround each of the large boulders within the marl basin.
The compression and distortion of marl deposits by the superimposition of the limestone boulders implies that the boulders arrived at the site during the mid-Holocene. The only forces capable of moving such massive lithics are glacial or anthropogenic. Since glacial influences had clearly subsided before the boulders were installed, human agencies are implicated by default.
Excavations carried out at Ballycahill uncovered a substantial artificial stone platform (c. 180m east–west by c. 27m). It comprised dark blue/grey siltstone, sandstone and conglomerate boulders interspaced with smaller rounded and thin fragment sand and silt stones. The sandstone and conglomerate boulders were believed to be naturally in situ and were incorporated into the platform structure. The large silt and limestone boulders appeared to have been laid with a preference for the flattest face at the surface. This positioning underlines the deliberate nature of the construction because under natural influences the boulders would settle on their broadest surface. It was suspected that they were specifically selected to combine to form a more or less level platform. The smaller cobbles were used to fill the gaps between the boulders and provide a continuous stone surface.
The maximum width exposed was 27m north to south; however, the platform continues northwards beyond the current CPO and has been truncated by the N7 to the south. A re-examination of the work carried out in the 1990s as part of the construction of the Nenagh bypass also suggests that similar large boulders were noted underlying the current N7, (TN020–117) and possibly further north as well (TN020–119). The true dimensions of the platform have therefore been lost. The quantity of siltstone boulders evident in the overburden landfill of the western field, as well as a substantial mound of displaced boulders on the south side of the N7; however, suggests that the original extent may have been considerable. It is hoped that a non-invasive probing survey will be carried out to trace the platform’s northern extent.
The site was subsequently covered by an amorphous peat layer which developed as a fen peat at the margin of a former wetland (now drained). The wetland can be roughly defined by the 50m OD contour. The sequence of marl under peat indicates the presence of standing water in the early Holocene with progressive infilling by peat to form a fen (base-rich wetland). The stratigraphic position of the Ballycahill platform suggests that the marl-peat transition may have occurred at about the same time as the platform was constructed. Unless the platform was intended to be permanently submerged, it also implies the water level dropped significantly between the deposition of the marl and the creation of the platform.
The scant artefact assemblage consisted of a shaped stone, two possible hammerstones, two sherds of post-medieval pottery and several fragments of unworked chert and flint. None of the finds were recovered from secure contexts.
Previous attempts to date the peat initiation from the surrounding basin gave inconsistent and contradictory results with date ranges from 8710–8460 cal bc to cal ad 760–900 (Radiocarbon dates from SUERC). Further site-specific dates are needed to confirm its age.
The unique Neolithic site of Tullahedy (TN020–079) was tantalisingly close. Excavations at the site recorded the deposition of high-status Neolithic material, including a 0.4m axe, and formal sculpting of the mound profile (McConway 1998; Kelleher forthcoming). That monumental landscape manipulation was carried out so close to the Ballycahill site allows for the possibility that such activities may have extended beyond the mound itself. The platform seems to formally fringe the water body which surrounds the important Neolithic centre. The fact that the culture represented at Tullahedy was expert in megalithic technology lends circumstantial weight to the argument that they may have been involved in creation of the platform.
Other prominent sites in Tullahedy include the motte and bailey (TN020–075) and tower-house (TN020–074). Remains from Ballycahill townland comprise the ruins of a castle and associated motte (TN020–084), a church and graveyard (TN020–082) and a holy well and bullaun stone (TN020–085). Ringforts have also been identified in Ballycahill (TN020–086) and nearby Lashesseragh (TN020–081).
Dating the construction of the platform is crucial to its interpretation. Post-excavation analysis and reporting is ongoing.
References
Kelleher, H. (forthcoming) Excavations of Neolithic enclosure and settlement. Tullahedy, Co Tipperary.
McConway, C. 1999 Unpublished summary excavation report, Licence No. 97E472.