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Summary Full report
Site Type: Coastal section
Site Status: ASSI
Grid Reference: D167463
Rock Age: Carboniferous (Dinantian)
Rock Name: Fair Head Tuff Formation
Rock Type: Conglomerate, Mudstone, Shale, Tuff
Fossil Groups: Arthropod, Plant
Other interest: palaeosol, No Data

Summary of site:

Most of the sedimentary rocks around Fair Head are buried in the accumulated blocks of dolerite which have fallen from the cliffs of the massive sill above. However, north of Faragandoo there is a small exposure along the shoreline which has yielded a unique assemblage of land arthropods entirely new to science.

About 10m of rock can be seen in this small section, starting with 3m of water-washed volcanic ash containing the root systems (called Stigmaria) of lycopod fossil trees, in places still obviously connected to their tree stumps. At the top of this bed there is a recognisable fossilized soil profile overlain by a thin coaly layer. There follows 0.3m of grey, indurated (hardened) mudstone containing beautifully preserved fronds and shoots of several species of seed ferns, among the finest Carboniferous plants ever collected in Northern Ireland. More volcanic ashes with sparse plant remains follow, in turn topped by 3m of ash with rootlets and nodules of carbonate minerals. More shales with rootlets follow and the topmost bed seen is a pink volcanic ash around 2m thick. The fossils at this locality have created much palaeontological excitement because they appear to represent many animals and plants never previously seen. Lycopod trees that grew in the Carboniferous forests had hollow stems that became buried as the trees died. The open tops of these tree stumps appear to have become natural traps or was perhaps the preferred living spaces of a variety of arthropods. In either event they became their final resting places. Remains of centipedes, spiders and almost perfectly preserved mites have been found; six new genera of mites, each with one species, have been described. The plant remains are also the subject of continuing research. The rocks at Faragandoo indicate a hot, humid environment in which lycopod trees and a rich flora of other plants thrived on the volcanic soils. The trees and leaf litter lying on the forest floor were alive with a prolific arthropod fauna. The hollow stumps and root systems of dead trees appear to have been either traps or the preferred niches for many arthropods, particularly a variety of mites. At this time the region was part of a large continent drifting at an infinitesimally slow rate northwards across the equator. The age of these rocks is middle to late Brigantian (around 335 million years old). Arthropod faunas from the preceding period, the Devonian, and from the late Carboniferous have been described, but there has been a tantalizing gap in the fossil record for the period between. This is the first time that Lower Carboniferous land dwelling arthropods have been seen. This fauna begins to fill that gap in the evolutionary sequence and gives a first glimpse of the ecology of the period. For these reasons Faragandoo is likely to play an important international role in our understanding of life at the close of the Visean epoch of the Carboniferous. The site is also nationally important as the only known exposure of these rocks. Only the sea presents a threat to this site and in the longer term it may reveal more than it destroys.

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