Glendesha ASSI

The area is of special scientific interest because of its geology, which is visible in an outcrop on the western side of Slievebrook. The Slieve Gullion volcanic complex, of which Camlough Quarry is a part, is the finest example of a Palaeogene igneous centre in Ireland and is among the best topographic expressions of a ring-dyke system in the British Isles. The rocks found here are of international geological importance, having played an important role in a number of theories related to the development of and interaction between igneous rocks.

The Slieve Gullion complex developed in an area of crustal weakness, previously exploited by the much older Newry granite, around 400 million years ago. The Slieve Gullion complex is historically important as it has featured in a number of major geological debates on the nature of igneous rocks and the processes by which they can be formed.

The main rock exposures found in Glendesha consist of the porphyritic felsite part of the ring dyke which here forms the steep hillside of Slievebrack.