section_path: Geography/Geology
section_name: Geology
paragraph_text: Geology
  
  The island consists of varied geological provinces. In the west, around County Galway and County Donegal, is a medium- to high-grade metamorphic and igneous complex of Caledonide affinity, similar to the Scottish Highlands. Across southeast Ulster and extending southwest to Longford and south to Navan is a province of Ordovician and Silurian rocks, with similarities to the Southern Uplands province of Scotland. Further south, along the County Wexford coastline, is an area of granite intrusives into more Ordovician and Silurian rocks, like that found in Wales.
  
  In the southwest, around Bantry Bay and the mountains of MacGillycuddy's Reeks, is an area of substantially deformed, lightly metamorphosed Devonian -aged rocks. This partial ring of "hard rock" geology is covered by a blanket of Carboniferous limestone over the centre of the country, giving rise to a comparatively fertile and lush landscape. The west-coast district of the Burren around Lisdoonvarna has well-developed karst features. Significant stratiform lead-zinc mineralisation is found in the limestones around Silvermines and Tynagh.
  
  Hydrocarbon exploration is ongoing following the first major find at the Kinsale Head gas field off Cork in the mid-1970s. In 1999, economically significant finds of natural gas were made in the Corrib Gas Field off the County Mayo coast. This has increased activity off the west coast in parallel with the " West of Shetland " step-out development from the North Sea hydrocarbon province. In 2000, the Helvick oil field was discovered, which was estimated to contain over 28 million barrels (4,500,000 m 3) of oil.