2008:1055 - Carney (O’Beirne), Sligo

Testing was recommended by GeoArc Ltd in April 2006 following a geophysical survey (licence 06R58) across a proposed residential development site at Carney, Co. Sligo. The geophysical investigation formed part of an archaeological assessment. SL008–060 (a ringfort) is located on the proposed development site. A 20m buffer zone around this monument had been incorporated into the proposed development plans. The geophysical survey identified several probable archaeological features in the north of the site including seven circular features interpreted as barrows. The proposed development was then redesigned to achieve preservation in situ of six of these features. The DoEHLG recommended phased testing across the site with the first phase designed to test the weaker geophysical anomalies in the southern part of the site.
Twelve trenches were opened using a tracked excavator. No archaeological features or finds were discovered during test-trench excavations. The strongest geophysical evidence for material remains (M20) was a particularly linear expression of bedrock. There was no evidence for what was suggested to be a remnant field boundary (M21). In this case we may speculate that any physical remains of the feature have been removed but that chemical residues persist creating in effect a ‘ghost feature’. Similarly the cultivation ridges have left only the vaguest of expressions in the soil and no associated cut features. A possible cut feature was found in Trench 5 which could have corresponded to M26. However, a similar feature oriented in the same direction was found in Trench 6 and it is likely that these were the same linear feature. Furthermore, it is likely that the feature was natural, as there were no finds, a barely discernible cut and little substantive difference between the cut and fill material. The presence of slate, degraded limestone, sandstone and sheet bedrock throughout the site also offers a partial explanation for the anomalous geophysical readings.
A second phase of test excavations took place between 3 and 6 June 2008. This phase concentrated on the northern part of the site where geophysical survey had indicated the presence of features including a linear ditch-like feature (M14) and several circular barrow-like features. One of these circular features (M7) was also tested. Testing found physical evidence for the linear anomaly M14, which ran from west to east in the field. This proved to be a ditch which was probably a former boundary ditch. This feature was found in Trenches 1 and 3. Modern pottery, glass and a clay pipe were found in the ditch. A number of smaller linear features were found across the site which, along with furrows and ploughmarks, are the result of modern agricultural activity. The site of M7 was tested by hand and nothing of an archaeological nature was found. One can only conclude that, as in the case of several of the anomalies tested in the southern field, the physical integrity of the feature has been destroyed but the soil has been chemically altered by its presence. This has led to the detection of ghost features. However, it begs the question as to why no trace survives even in the natural. The answer must be either that the feature was particularly shallow and did not cut the natural or there was never a barrow in this location and the anomaly is from another circular feature, which has been destroyed. A deposit which was interpreted as displaced or redeposited fulacht fiadh material was found at the junction of Trenches 4 and 5. This may be evidence of a levelled burnt mound in the area. subsurface features may have survived but there was no geophysical trace of a substantial feature such as a trough or ancillary pit.
A third phase of test excavations was carried out between 25 and 30 August 2008. This phase of testing was concerned with a cluster of barrow-type features in the north of the site and was carried out by hand. Five test-trenches were opened revealing twelve possible features which were investigated by means of half sections. However none of these features proved to be archaeological. The question then arises as to why there was no physical evidence of the circular features which were so clearly identified by geophysics. The first possibility is that the features were incorrectly targeted, that the trenches did not catch them. This can be discounted on the basis that the geophysical survey grid was accurately recreated. The trenches were in the right place. The second possibility is that the features were present only in the topsoil and there would be no trace in the natural. This cannot be discounted but does not explain why there was no trace of the features in section. Moreover, modern finds were presenting in the lowest levels of topsoil throughout the site. The final possible answer is that what the geophysics recorded were ghost features. These ghost features are shallow cut and fill features which have not cut the natural and whose physical integrity has been destroyed by agricultural or other work. The soil, though disturbed and no longer within a cut and fill context, retains an altered chemical signature and gives a coherent reading to the geophysical survey equipment. This is quite common with agricultural features such as furrows and indeed was the case in the southern area of the proposed development. This would suggest that the entire area has been thoroughly ploughed out. There was also evidence of levelling in the field probably datable to land improvements of the 18th and 19th centuries.