This abandoned quarry is of interest because it exposes the most easterly outcrop of the Ballyshannon Limestone Formation in Northern Ireland. The rocks here, mostly pure to silty limestones with some shales, are close to a major fault zone and fault planes with movement striations (slickensides) brecciation (shattering into angular pieces) and intense fracturing have created cavities that have since been obliterated by the mineral calcite. All the limestones have been recrystallized by the structural disturbance and although fossils are sparse, corals have been identified that give an Arundian age, about 345 million years ago, towards the middle of the early Carboniferous.