Pollen and spore assemblages from the oligocene Lough Neagh Group.

This study was initiated to solve a stratigraphic problem for the Geological
Survey of Northern Ireland prior to the revision in 1997 of the 1:250000 map of the
solid geology of Northern Ireland.
An exploratory drilling programme carried out by the Survey in 1983/1984
revealed the existence of previously unknown Tertiary sediments north west of the
Tow Valley Fault. The boreholes revealed a sequence of clays and lignites that were
attributed to the Lough Neagh Group. These lay above an interbedded sequence of
litho marge, pyroclastics and lacustrine deposits termed the Dunaghy Formation.
The Geological Survey required an age to be assigned to this formation and it
was proposed that the use of the preserved pollen and spore assemblages offered the
best means for dating the sequence. In order to achieve this four boreholes were
analysed. Boreholes 13/611, 13/603, 36/4680 and 27/415 contain the Lough Neagh
Group. In addition 13/611 and 13/603 contain the Dunaghy Formation.
From the pollen and spore assemblages recovered an Oligocene age IS
confirmed for the Lough Neagh Group and proposed for the Dunaghy Formation. This
information led to the attribution of an Oligocene age to the Dunaghy Formation in the
1997 revised 1:250000 Geological Map of Northern Ireland.
The palaeovegetation deduced from the recovered pollen and spore
assemblages is in accordance with an Oligocene cooling. The climax angiosperm
vegetation, predominantly consisting of temperate forms with some megatherm taxa,
grew in a raised bog forest ecosystem within a fluvial-lacustrine environment.
All pollen and spore taxa recovered are described including new forms
identified. A correlation of the four sections is proposed.