geological time periods

Quaternary

Ireland's landscape was formed during the … . There have been a number of glacial events, the last one in Ireland ending around 12000 years ago. The ice-shaped mountains, glaciated valleys and deposits in the form of eskers and drumlins all formed due to these glacial events, and they also they also left the foundations for our waterways and bogs. (2.6 Ma- present, Icehouse)

Palaeogene

​This Period saw the opening of the North Atlantic Ocean and the associated generation of volcanic and magmatic rocks. … age rocks are mainly found in the north eastern part of the island and form the prominent features of the Cooley Mountains, Co. Louth, the Slieve Gullion ring dyke which straddles the Ireland-Northern Ireland border between Co. Armagh and Co. Louth, the Mourne Mountains, Co. Down and the Antrim plateau. (66-23 Ma, Hothouse-Icehouse)

Cretaceous

​Rocks from the … are only found in Northern Ireland. They may have formed on other part of the island but have since been eroded. They survive along the Antrim coast because the overlain and therefore protected by the Antrim basalts. Most of Ireland was covered by a sea during this period and therefore the remaining rocks are white limestone (or chalk) rich in fine marine fossils. (145-66 Ma, Hothouse)

Jurassic

​The continent of Pangaea continued to break up during the … Period and Ireland was mainly dry-land apart from the northeast and southeast which were shallow seas. … rocks are mainly found in exposed along the Antrim coasts and are rich in marine fossils including the reptile ichthyosaur. Pockets of … clays have been found in other parts of Ireland including in Cork and Kilkenny. (201-145 Ma, Hothouse)

Triassic

​Ireland was part of a desert during the … and fine-grained red sandstone and siltstone was deposited. These are found in one area on the Cavan/Meath/Monaghan boundaries and on Co. Down and Co. Antrim. (252-201 Ma, Hothouse)

Permian

​Ireland was just north of the equator during the … and was a low-lying arid area. Fine desert red sandstone and coarser conglomerates were deposited. Cycles of shallow seas and high evaporation rates occurred towards the end of the …. The Kingscourt gypsum and the Antrim salts are from this time. (299-252 Ma, Icehouse)

Carboniferous

​… bedrock accounts for over half the area of Ireland - it is found in every county apart from one. In the early …, Ireland was periodically covered in shallow tropical seas and fossil-rich limestone formed. Later, sea level changes meant the development of coal in Co. Roscommon and Co. Kilkenny. (359-299 Ma, hothouse-icehouse)

Devonian

​There are two rock types associated with the … in Ireland - the Caledonian granites and the Old Red Sandstone. The Leinster, Galway, Donegal and Newry granites and other smaller bodies intruded with the final closing of the Iapetus Ocean. Ireland was in the southern mid-latitudes by this time, sedimentary basins formed and with the high sediment supply from the Caledonian mountains to the north, large deposits of sandstone (Old Red Sandstone) formed. It is seen mainly in Cork and Kerry. (419-359 Ma, Hothouse)

Silurian

​This period is marked by the deposition of huge volumes of sediment in various terrestrial and marine environments and also by volcanism. The Iapetus Ocean closed completely during the … and this is reflected in the sedimentation. Sedimentation was continuous from the Ordovician into the … as seen in the Longford-Down terrane. … sediments are also seen in Mayo and Kerry. (444-419 Ma, Icehouse - hothouse)

Ordovician

​The Iapetus was closing during the … with the subduction of plates and the generation of volcanoes and earthquakes. Mountains, possibly as high as the modern Himalayas, rose to the north, and there was an increase in sediment being carried by rivers into the closing seaway. The sedimentary rocks deposited in the Precambrian were folded and underwent metamorphism during the … also. (485-444 Ma, Greenhouse-icehouse)

Cambrian

​The land we now know as Ireland was covered by an ocean we call the Iapetus Ocean during the … Period. The ocean separated two continents, Laurentia and Gondwana. Rocks from this Period were deposited in the sea and have our earliest known evidence of life in the form of trace fossils. Trace fossils are the preserved tracks or feeding tunnels of organisms. … rocks are found on Howth Head, Co. Dublin, Bray Head, Co. Wicklow, and in Co. Wexford. (541-485 Ma, Hothouse)

Precambrian

​The oldest rocks in Ireland are 1.7 billion years old and are found on the island of Inishtrahull, Co. Donegal. In Ireland, all rocks from the… have become metamorphic rocks during a later Period. We find rocks from this Period in west Co. Galway, Mayo, Sligo, Donegal, Tyrone and northeast Antrim, and in small sections of Co. Wexford and Co. Waterford. (4600-541mya) (variable climate)