SOCIETY AND SETTLEMENT IN GLENDALOUGH ... - Ian Cantwell

CHAPTER 1PALEOCOLOGY AND ARCHAEOLOGYGeologyThe origins oftheWicklow Massifdate back to when the Caledonian orogeny intrudedlarge batholiths ofgranite into the overlying Ordovician shales, slates and mudstones.In the process metamorphic schists were formed with veins of intruded metal ores,such as gold, copper and lead which were to play a part in the subsequent economicgeography ofEast Wicklow. In the subsequent 390 million years the overlying rockswere weathered and eroded which resulted in peaks ofgranite and quartz in the centreofthe chain and sedimentary rocks on the flanks separated by a metamorphic aureole.The fact that parts of the aureole survive on some mountain peaks indicates that thearea has been through a period of recent tectonic uplift which speeded up thedenudation processes. To the north and east a ridge of Cambrian quartzite mountaincones (c. 500m)border the mountains from the northern Leinster and easternlowlands]. The Vartry Plateau is Deshaped,bounded on the west by the granite massifridge (650-800m) and by a semi-circular quartzite' ridge (250-43Om) with severaldrainage exits.DrainageThe mainriver valley system is the north to south Avonmore river, whose source is tobe found in the Sally Gap (c. 49Om). The Avonmore is mainly fed by the tributaryrivers ofthe Glenmacnass, Glendassan and Glendaloughvalleysas wen as rivers furthersouth before joining the sea at Arklow. The Vartry plateau is drained by a river ofthesame name which exits at the Devil's Gl~ a gorge ofglacial origin. 2 This river maylWhidow1.B., Geology andscenery In Ireland, London, 1974, pp.263-712Whit1ow, op.cit., pp. 263-7111