Rocks in the Ballymote area, occupying one of several broad downwarps of inherited caledonoid trend, provide a crucial link between Viséan successions north of the Highland Boundary line (represented locally by the Ox Mountains) and successions to the south, part of the extensive 'shelf' limestone of central Ireland. The sequence, exceeding 1070 metres (3500 ft) in thickness, ranges in age from early to latest Viséan 21to 2) and is succeeded, generally without interruption, by thick upper Carboniferous shales. The succession of different rock types reflects changing controls in the sedimentary environments of a shallow shelf sea. The main episodes (some repeated) include the deposition of locally-derived conglomerates and sandstones in a partly enclosed basin; the accumulation of various thick, clear-water limestones, partly in continuation with adjacent basins; and the influx of muddy detrital sediments from a more distant source.
The rocks contain a succession of rich and diverse benthonic faunas, predominantly of corals and brachiopods, but near the top these give way to several distinctive goniatite-lamellibranch faunas.