A revised Mississippian (Courceyan – Chadian) geology of the Clogher Valley, counties Fermanagh and Tyrone (Northern Ireland)

Abstract:Following a geological research programme in 1998-2000, the Mississippian succession in the Clogher Valley has been revised and important new detail has been revealed. Immediately overlying the terrestrial Ballyness Formation, the interval originally ascribed to the Clogher Valley Formation has been subdivided into three new formations: the Clogher Valley Formation sensu stricto, the Fardross Sandstone Formation and the Moysnaght Limestone Formation. This sequence is overlain by the Ballyshannon Limestone Formation. The lithostratigraphy of these units is described and previous biostratigraphic work is reviewed and supplemented with new data. These indicate that the top of the clastic redbed Ballyness Formation is close to the Devonian-Carboniferous boundary, whilst the following marine succession ranges in age from the late Courceyan through to the Chadian. The thickness, nature and distribution of evaporite horizons in the succession is described. The provenance of various sandstones within the sequence has been assessed and lateral facies changes and thickness variations in the succession are attributed to syn-depositional tectonic activity.