Ballypalady
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Geology & landscape
Rock Type: Basalt, Ironstone, Shale
Landscape processes: Volcanic / Igneous
Description
Ballypalady Tertiary palaentology Ballypalady is the best known, best documented and botanically the richest of the Tertiary Interbasaltic fossil plant localities in Ireland. As all the other sites that historically yielded fossil material were associated with underground mine workings, Ballypalady is also the site most suitable for future studies. The time interval between emption of the Tertiary Lower Basalts and Upper Basalts is referred to as the Interbasaltic Member. These events date from the Palaeocene epoch, some 60 million years ago. During this period, weathering of the Lower Basalts predominated, including transportation of plant material. The Ballypalady Plant Bed was deposited by flood-bome sediments, which were derived from the weathering and erosion of the adjacent Lower Basalts. Repeated minor flood events buried a rich variety of plant debris that subsequently decayed to leave well-preserved moulds within the iron-rich clastics. The plant bed has a silty to rather gritty texture, the sand-sized clasts being of a creamy, brick-red or grey colour. Bedding plane spacing in this material is typically between 5 and 20 mm. The plant material occurs largely as impressions, with traces of carbonaceous material present in the finer sediment. Cavities left by the decay of woody plant fragments can be common in the coarser units. The flora at Ballypalady is abundant and moderately diverse, including conifers, angiospenns flowering plants and pteridophytes fems, with both fruiting structures and vegetative material present for some. Several new taxa were described from the site including Pinus plutonis, Pinus bailyi, Tsuga heerii and Taxus swanstoni. The angiospenns are much more poorly documented than the gymnosperms, although it is evident from the range of leaf morphologies and venations present that several distinct species are included. The site has also yielded contemporary pollen, and includes pollen from species of alder Alnus spp. yew Taxodiaceae and also types similar to modem Pinus, Picea or Podocarpus together with pollen of Sciadopitys-type and of the 'atumescens'-group. The railway cutting exposures are of basalt but include a low mine entrance which shows an ironstone passing up into a coarsely laminated unit immediately beneath the overlying Upper Basalt. There is also a clear exposure of a coarsely and irregularly laminated rock containing dark lenses of shale-like material interbedded with many pale slivers of rhyolitic and glassy material. The whole unit has the appearance of an ignimbrite and dips gently eastwards towards the mine. Palynological and macro floral evidence for the age of the Ballypalady plant bed is consistent with the Palaeocene age of basalt emplacement as deduced from radiometric dating. The floristic assemblage has been assigned to the Arcto-Tertiary flora of warm-temperate conditions. The Ballypalady Plant Beds, together with a number of other less diverse sites are of considerable importance, both from a palaeobotanical view and for gaining an understanding of regional palaeoenvironments during this time interval. Such plant beds can also be important in correlation of Tertiary stratigraphies between Northern Ireland and elsewhere. https://www.daera-ni.gov.uk/publications/ballypalady-assi