Editing County Wicklow (section)

===Geology===
The Wicklow Mountains are centred on the Leinster [[batholith]] and are primarily composed of [[granite]] surrounded by an envelope of [[mica]]-[[schist]] and much older rocks such as [[quartzite]]. Covering {{convert|1,500|km2|mi2}}, the Leinster batholith is the most expansive mass of [[Intrusive rock|intrusive]] [[igneous rock]] in Ireland or [[Great Britain|Britain]].<ref>{{cite journal | location = UK | url = https://jgs.lyellcollection.org/content/175/2/229 | title = Multiple intrusive phases in the Leinster Batholith, Ireland: geochronology, isotope geochemistry and constraints on the deformation history | journal = Journal of the Geological Society | year = 2018 | publisher = Geological Society of London | doi = 10.1144/jgs2017-034 | access-date = 24 August 2021 | archive-date = 24 August 2021 | archive-url = https://web.archive.org/web/20210824025241/https://jgs.lyellcollection.org/content/175/2/229 | url-status = live | last1 = Fritschle | first1 = Tobias | last2 = Daly | first2 = J. Stephen | last3 = Whitehouse | first3 = Martin J. | last4 = McConnell | first4 = Brian | last5 = Buhre | first5 = Stephan | volume = 175 | issue = 2 | pages = 229–246 | bibcode = 2018JGSoc.175..229F | s2cid = 134435310 }}</ref> The oldest rocks in the county are the quartzites of the Bray Group that include [[Bray Head]] and the [[Little Sugar Loaf]] and [[Great Sugar Loaf]] mountains.{{sfn|Holland|2003|p=22}} These [[metamorphism|metamorphosed]] from [[sandstone]] deposited in the deep waters of the primeval [[Iapetus Ocean]] during the [[Cambrian]] [[period (geology)|period]] (542-488 million years ago).{{sfn|Jackson|Parkes|Simms|2010|p=142}}

As with much of Ireland, Wicklow's terrain was sculpted by successive periods of glaciation during the [[quaternary]]. Weathering and erosion by ice carved out long valleys known as [[glens]] (from the [[Irish language|Irish]] ''gleann'') such as [[Glenmacnass Waterfall|Glenmacnass]], [[Glen of the Downs]], [[Glenmalure]], [[Glen of Imaal]], [[Glencree]] and [[Glendalough]]. The Irish Sea Ice-Sheet began to retreat shortly after the [[Last Glacial Maximum]] ca. 20,000–23,000 years ago but significant ice masses persisted in the Wicklow Mountains for another 4,000–7,000 years.{{sfn|Tomkins|Dortch|Tonkin|Barr|2017|p=6}}