The name Desertmartin Limestone Formation was first used by the GSNI in 1983 for the outcrop of late Vis‚an limestones in the area around Desertmartin (1:50,000 Sheet 27). No information regarding the precise age of these limestones was presented nor was a stratotype locality selected. Although it is known that the limestone formerly was worked in many quarries these are all now closed and it is not known how many of them have been infilled since the resurvey of that area was completed in 1970.
The quarry located on the SE face of Drumbally Hill (H845 935) has been flooded at the NE end but, in the SW part, still exposes limestones that are typical of the Desertmartin Limestone Formation.
The quarry is located 1.9km NW of Desertmartin. Although formerly stretching for almost 300m around the base of Drumbally Hill, on its east side, most excavations are infilled and the only remaining open quarries now occur on the SE side of the hill. Some 3m of limestones are exposed in the remaining face inclined at 15 deg. to the SE. Bedding thickness is variable but is always undulose and is shale-free. The limestones are variable, coloured pale fawn grey and medium-grained but are usually stained pale purple-red on most surfaces, probably as a result of downward percolation of later Mesozoic groundwater. Medium to coarse grainstones dominate the sequence here, with thin layers of very sandy limestone and a report of quartz pebbles scattered occasionally in the rock. At the west side of the flooded part of the quarry complex are interbedded grey dolomitic (?) sandy limestones and thin black silty shales.
A sparse, often fragmented macrofauna of crinoid ossicles and large productid brachiopods, in particular Linoprotonia hemisphaerica is recorded from the limestones but corals are absent from this, and most other quarry sections, in the Desertmartin area.
