Torr Head ASSI

Protected area type: Areas of Special Scientific Interest
Feature type: 
  • Earth Science
  • Antrim
Council: Causeway Coast and Glens
Guidance and literature: Torr Head ASSI

Torr head is the best exposure of metamorphosed Limestone of Dalradian age in Northern Ireland. Torr head is the type locality for the Torr Head (Limestone) Formation. The site is of international importance as it is crucial in aiding the understanding of the relationships between rock sequences elsewhere in Northern Ireland and Scotland.

Some 600 million years ago sediment accumulating within an ancient ocean basin formed rocks which were later incorperated into an enormous mountain range. The residual core of this chain forms the uplands of North East Antrim, as well as the Sperrin Mountains. During this process the rocks were altered through the actions of temperature and pressure. In the case of the sequence at Torr Head the rocks were all altered and literally turned upside down.

The Torr Head formation is best viewed from the southern side. Here parallel limestone layers of the Torr Head Formation overlie a series of altered sandstone (the Altmore Formation). At the top of the limestone section a massive metabasite extends at least 50m to the top of Torr Head. This sequence of rocks records the development of a shallow sea, along the margins of Laurentia (a former continent, roughly equivalent to North America today), approximately 600 million years ago. Volcanic activity at the time has resulted in the association of limestone and basaltic rocks, which can now be seen at Torr Head. 

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