Limehill Farm
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Geology & landscape
Geological Period: Silurian
Description
Limehill Farm Silurian stratigraphy The shales at Limehill Farm are of Lower Silurian, Llandovery, age, about 420 million years old. The shales contain a graptolite fauna, but differ from typical Llandovery graptolitic rocks by also having a shelly element comprising bivalves and brachiopods. This is one of only two sites in Northern Ireland where shelly fossils of Silurian age occur. The locality is of historical interest as it was first recorded by one of the pioneer Irish geologists, Major-General Portlock, in 1843. Limehill Farm is the type locality for the internationally recognised zonal graptolite Monograptus sedgwickii. Graptolites were colonial marine organisms, while zonal fossils are used world wide to determine the relative age of rocks in which they occur. A number of other graptolite species were first described from here. In addition, the site has yielded the world's most ancient nowakiid to date, Nowakia brevis, for which this is also the type locality. Nowakiids are an extinct group of primitive molluscs. https://www.daera-ni.gov.uk/publications/limehill-farm-assi