Summary of site:
Ballagh Quarry is now little more than an infilled pit, largely built over, but the remaining outcrops give access to a crudely laminated, coarse-grained limestone made of crinoid fragments with a few brachiopod shell fragments. Limestones of this type are typical of shallow water environments with much current or wave action. The upper and lower limits of these limestones cannot be seen at Ballagh but are clearly exposed on the inaccessible upper face of Rockfield Quarry, immediately below the Meenymore Formation. Here 5-6m of pale to medium fawn/grey rock in very thick beds can be clearly identified. These rocks at both sites are the only examples of the Ballagh Limestone Member of the Dartry Limestone Formation and, because it is accessible only at Ballagh Quarry, this locality is the stratotype section (the typical representative of a named rock unit).
The Ballagh Limestone Member is significant because, unlike the fine lime muds usual in the Dartry Limestone, it was almost certainly formed in shallow water. Because it sits on deeper water muds, and is also topped by them, it is thought that the rock may have been transported into deep water from a shallow sea margin rather than formed in place.