Abstract The basal, dominantly littoral, part of the Courceyan (Dinantian, Early Carboniferous) Naval Group is described in borehole N866 from the Tara Mines area, Navan, County Meath, Ireland. The kerogen assemblages of 17 samples from the sequence are described in terms of the palynofacies they represent. Both the depositional environments and palynodebris deposited within them reflect distance from terrestrial source, which became more distant with time. The change in littoral sedimentation from dominantly siliciclastic to dominantly carbonate, near tthe top of the Liscartan Formation, represents drowning of the principal siliciclastic source areas on the margins of the Irish Midlands during the Courceyan (PC Miospore Biozone time). Spore colours and UV fluorescence indicate that the Navan area was not heated as much as other areas of the Irish Midlands.