The Moneymore complex is one of the few lowland locations recording the presence of fine-grained, glaciolacustrine sediments in Northern Ireland. The areal distribution of ice-marginal glaciolacustrine deposits along the western margin of the Lough Neagh lowlands, and the palaeoflows from these deposits show that the area records the approximate position of the western margin of the ice mass occupying the Lough Neagh basin at the end of the last glacial period. The basin thus formed one decay centre for ice in the east of Northern Ireland. Ice and snow melt in the uplands (Fintona Hills) to the west provided meltwater for limited erosion, transport and deposition of glaciolacustrine detritus in an ice-marginal waterbody ponded at 60m O.D. in the lowlands. Subsequent falls in lake levels were followed by partial dissection of the deposits. The undulating and deranged nature of the western Tyrone drumlin field also resulted in the formation of localised ice-proximal water bodies and the deposition of small glaciolacustrine sequences possible at a slightly later phase. The Moneymore Complex is subdivided into two sub-units: the Moneymore composite delta and the Annahavil delta.
The deposits of the Moneymore complex record glaciolacustrine deposition at the margin of a largely stagnant ice-mass situated in the Lough Neagh lowlands. The wastage of the ice mass and ice and snow melt from highland areas to the west provided meltwater and detritus which became impounded along the ice margin and at the end of the meltwater channels from the highlands. The heights of the upper surfaces of the sediments indicate that two extensive ice-marginal lake levels (61m O.D. and 110m O.D.) existed in the proglacial area. Where local topography allowed, smaller localised levels existed before and after the ponding of meltwater at these levels and is recorded by spatially restricted glaciolacustrine sequences. Later drainage of the lakes resulted in the subaerial erosion and dissection of the deposits.
