On the 1947 to 1948 revision of the Ordnance Survey six-inch map, a hachured feature, that is, a cluster of short lines used by mapmakers to indicate a depression or earthwork in the terrain, was marked at this location. It had the visual grammar of something ancient, the kind of notation that might signal a ringfort, a collapsed souterrain, or some other remnant of earlier occupation. When someone finally visited the site in 1985, the feature turned out to be a disused quarry, almost certainly post-1700 in origin, and therefore considerably more recent than the ancient monuments that tend to attract archaeological attention.

The gap between the map marking and the ground inspection is itself part of the interest here. For several decades, the hachured symbol sat in the archive, its meaning unresolved. Quarries of this period were working features of the rural landscape, used to extract stone for field walls, farmsteads, and roads, and they rarely earn the kind of formal record that a prehistoric monument would receive. Because the Treanbaun quarry post-dates AD 1700, it falls outside the scope of archaeological protection, which in Ireland generally concerns itself with earlier remains. It is the kind of place that exists in the gap between archaeology and industrial history, too recent for one and too modest for the other.