Glendalough, Co. Wicklow

The Glendalough Valley is a deep glacial valley in the central Wicklow Mountains. The mine site within it sits at the head of the Upper Lake, where siltation has led to development of a wetland. ‘Van Diemen’s’ Land is an isolated mine site further up the valley, on high ground.

Geological System/Age and Primary Rock Type
The bedrock is Lugnaquillia Granodiorite, part of the Lugnaquillia Pluton which is one of the five plutons that comprise the late-Caledonian (405 Ma) Leinster Granite batholith. The granite is cut by slightly younger quartz veins containing lead and zinc mineralization. The contact between the granite and schists of the Lower Palaeozoic Maulin Formation runs through the site immediately east of the mine area. The valley itself and the glacial features within it date from the last Ice Age.
Main Geological or Geomorphological Interest
Glendalough is a marvellous example of a glaciated U-shaped valley, with oversteepened cliff sides and a flat floor. At the mouth of the glen where it meets Glendasan is a delta, which formed at the end of the last Ice Age in a lake that reached a higher level than either of the present lakes. Above the delta, to the north, is a fine medial moraine deposited between the ice of the Glendalough and Glendasan glaciers as they decayed during deglaciation. The two lakes at Glendalough are separated by a broad, low alluvial fan deposited by water from the high level valley to the south of Glendalough. At the upper end of the Upper Lake, at the so-called “Miners Village”, is a modern delta building out into the lake, which is in turn gradually shrinking in size.

More specific trip details to follow here shortly….