1976:043 - BIG GLEBE, Derry

The mound at Big Glebe, 1 and 1/2 miles inland from Mussenden Temple, near Castlerock, was larqe and well-preserved. Its flat summit, 20m in diameter, was over 7m on average above the general level of the surroundings. In plan the mound was oval and the diameter across the ditch was more than 70m. It was described over 140 years ago in the Ordnance Survey Memoir for the Parish of Dunboe, and a useful sketch drawing was appended. Complete excavation was necessitated by the impending removal of the mound for agricultural “improvement”.

The excavation showed that the mound had probably been constructed and lived on during the Early Christian period. Certainly the people who fortified themselves on top of the mound left behind no relics, weapons or implements of Anglo-Norman type. The perimeter of the earthen mound had been defended by a roughly circular wall built of unmortared loose stones, 1.5m thick on average and up to 1 m high at present. 

There were signs of a gap on the S side corresponding with the position of the entrance mentioned in the OS Memoir. Nearby were the remains of a “souterrain” or underground, stone-built refuge. It was 10m long and the outer edge of the low passage was formed by the inner face of the perimeter wall. The structure had originally been hidden beneath a mound carefully faced the small slabs laid horizontally.

At the central, highest part of the mound and isolated from the perimeter wall the burnt outline of a circular house 8.5m in diameter was uncovered. The structure was perfectly circular and the 111 stakeholes which defined its perimeter wall averaged 7 or 8cm in diameter. A very surprising feature of the structure traces uncovered was the great depth of the stakeholes, 55 to 65cm. No comparable structure has so far been recognised elsewhere. The dwelling is envisaged as having the long pointed stakes driven into the comparatively loose soil of the freshly constructed mound which were then woven around with wickerwork (leaving no trace) and perhaps covered by a conical roof of branches and thatch securely laced into position on top of the wall. There was a paved entrance to the house on the E side and numerous internal stakeholes and pits. The internal stakeholes may represent the positions of roof-supports or anchored items of furniture but no coherent sense can be made of their distribution at present. The outlines of two further structures apparently ancillary to the large central house were found. One was defined by a curving gully 15cm deep with occasional large stones in its fill, the other was indicated by a D-shaped platform carefully constructed of small boulders. The only finds associated with the structures, or indeed from the entire mound were sherds of “souterrain ware”, fragments of two bronze pins and a quern. All the objects were of Early Christian type and one would expect to have found them in a rath rather than on the top of a motte-like mound.

When the structures on the top of the platform had been excavated it was decided to remove a quarter of the mound entirely to see if it contained evidence of earlier phases of occupation or of its method of construction. The NE quadrant was largely removed at this time and in it were found the remains of a sloping ramp, retained on the N by neatly built angular stone blocks leading up to a curving dry-built wall 3m high. At first this was thought to represent another smaller masonry revetted structure later enclosed within the dumped earth of the final mound. It was decided at this stage to excavate the entire mound in case this masonry turned out to be part of something really unique. It was discovered that the masonry did not extend within the mound any further than had already been revealed. If a different type of monument had preceded the mound then it had been very thoroughly destroyed before the earth was heaped up over it. No traces of any such demolition were found and it is likely that the ramp and short length of wall running at right angles represents a method of construction for the earth mound enabling larger volumes of soil to be carted up to the summit and dumped than could be emplaced by hand.

When the mound was being completely cleared away it became apparent that it had been erected all in one continuous sequence. The original topsoil, buried under the mass of the mound, itself sealed scattered traces of prehistoric occupation — pits, hearths and postholes, but these were clearly ancient and invisible by the time the mound was built. The mound was composed of largely horizontal layers of clay and, near its base, layers of small stones derived perhaps from the surrounding ditch and from field clearance nearby. The ramp mentioned above and its associated wall had been built on top of an intermediate stone layer when the mound was already over 1.5m high.