A MAP R AGE PERIOD MAIN ROCK TYPES ENVIRONMENTS TECTONIC EVENTS E COLOUR Ice Age: Ireland covered and shaped by ice. 1.8 Quaternary* C I Lake & swamp: Mid-Tertiary clays and lignite deposited in O Geology of Ireland Z large lake (the precursor to L. Neagh). O Clay Tertiary North Atlantic rifting: Greenland separates from N E Volcanoes: Vast amounts of basalt lava flood NE Ireland Europe as Atlantic rift extends northwards. 1:1,000,000 scale C during Early Tertiary. Basalt 65 Geological Survey of Ireland Chalk Shallow 'Chalk sea': Ireland is land area for much of time. Compiled by B. McConnell, S. Gatley & A. Sleeman. Cretaceous Pure limestone deposited in late Cretaceous shallow sea, probably over whole of Ireland. Simplified from the Geological Survey of Ireland 1:100,000 scale Bedrock Map Series (1993 - 2003) and the Geological 144 C I Early Atlantic rifting: American & European Plates 1. The Giants Causeway: Tertiary basalt lavas Survey of Northern Ireland 1:250,000 scale Geological Map O Z Sea basins: Mud and limestone deposited in early Jurassic begin to separate, forming Atlantic ocean between. of Northern Ireland (1997). O shallow sea in NE, while rest of Ireland is land. Thick Z Jurassic E accumulations of sediment as today's offshore basins M form. Shale & limestone 203 Ó Geological Survey of Ireland 2003 Extension: Marine basins around Ireland formed by stretching of the continental crust. Triassic Desert: Red sandstone formed in arid desert dunes and Photograph credits: 1- GSNI; 2- B. Long; 3- B. McConnell; playa lakes. Evaporite (salt & gypsum) in hypersaline lakes. 4- M. Pulsford; 5- C. MacDermot; 6 & 7- M. Parkes 250 Sandstone 'New Red Sandstone' Variscan Orogeny: Minor effects in Ireland of Permian River deltas & swamps: Sand and mud deposited in large mountain building in Central Europe. river delta systems advancing into sea. Coal formed in hot 298 swamps. N Sandstone & shale Tropical sea: Limestones deposited in warm tropical sea. 50km Carboniferous Limestone Advancing sea: Sand and mud deposited in shallow sea Sandstone & shale advancing from south to north over eroded Devonian 354 mountains. C I Mountains & rivers: Red sand and mud deposited among O Sandstone Z Devonian 'Old Red Sandstone' semi-arid mountains by large river systems. Subsiding O basin in SW receives vast thickness of sediment. Acadian Orogeny: Mountain building as Iapetus 2. The Poisoned Glen: ice-sculpted Donegal granite E A finally closes, joining NW and SE halves of Ireland. L 410 A P Ocean basin: Sand and mud deposited in narrow ocean Silurian Sandstone & shale basin and continental margins as Iapetus closes. 440 Sandstone & shale Ocean depths & Ring of Fire: Sand and mud deposited in Ordovician Shale & sandstone, 1 deep ocean by turbidity currents. Ring of volcanoes Grampian Orogeny: basalt & rhyolite Mountain building and around ocean formed above subduction zones metamorphism in NW as volcanic arc collides with continental margin when Iapetus begins to close. 495 Sandstone & slate Shelf sea: Sedimentary rocks deposited on continental Cambrian Quartzite in above shelf in SE. Iapetus ocean opens: Ancient continents rift apart 545 to form Iapetus ocean crust between. Schist & gneiss Ancient continents: Ireland's oldest rocks formed 1800- 1900 million years ago as igneous intrusions; Cadomian Orogeny: Metamorphism of oldest rocks 2 Derry Quartzite in above metamorphosed to gneiss by Grenville mountain building. in the SE. PRECAMBRIAN* Sedimentary rocks (Dalradian), including deposits of global Grenvillian Orogeny: Mountain building and ice age, formed at rifting continental margin in NW. metamorphism of oldest rocks in the NW. Letterkenny * Precambrian and Quaternary not to scale IGNEOUS ROCKS Kilroot Basalt, minor rhyolite - Tertiary Gap in geological record salt Volcanic rocks (no rocks preserved) Volcanic rocks - Precambrian to Carboniferous Working mine or pit Granite & gabbro - Tertiary Belfast 2 Photograph location Granite - Ordovician to Devonian Intrusions Cavanacaw gold Gabbro & related rocks - Ordovician Monaghan Sligo Ballina Dundalk Cavan Kingscourt gypsum 3. The Twelve Bens: Dalradian quartzite mountains Castlebar Navan zinc, lead 3 Tuam Mullingar Athlone Dublin Galway Tullamore 4. The Burren: karstic Carboniferous limestone 4 5 Ennis Galmoy zinc, lead Lisheen Limerick zinc, lead Kilkenny 5. The Cliffs of Moher: bedded Carboniferous sandstone Wexford Tralee Waterford 7 Mallow Killarney 6 Cork 6. Valentia tetrapod tracks: early 7. Booley Bay: striped Cambrian mudstones, an amphibian footprints preserved in Devonian sandstone important fossil site.