The deposits of the Lough Fea platform record the phased decay of an ice lobe from this upland structural depression and the strong influence of bedrock topography on the patterns of local ice marginal retreat. Ice marginal ridges and kame terraces mark the successive positions of a downwasting and backwasting ice mass. The ice, subject to bedrock control and ice pressure, split during the process of retreat to form two discrete ice lobes. Sediments of the western part of the glaciofluvial complex were partially supplied by the north-northeast to south-southwest trending Davagh esker complex, which conducted subglacial meltwater and debris northwards from the Ballinderry valley lowlands, against the local topographic gradient. The complex comprises 17 subunits covering the Lough Fea platform and the flanks of the upper Moyola valley as follows: Crockandun Terrace, Corick Terrace, Carnabane Ridge and Terrace, Brackagh Ridge and Plain, Slaught Ridge, Stone Hill Ridge, Mill Lough Ridge, Teal Lough Plain, Davagh Ridge Complex, Black Lough Ridge, Ballybriest Ridge, Lough Fea Depressions, Grouse Lodge Ridge, Lissan Ridges and the Moyola Valley, and Disert Ridges.
The landform and sediment assemblages are inferred to represent ice-marginal deposition during the phased deglaciation of the Lough Fea platform. It is inferred, from both the local granitic and basic igneous erratic content of the deposits and the evidence of ice movement patterns from adjacent areas, that the area was occupied by ice of southerly origin during the last glacial cycle. During the deglacial cycle, ice on the Lough Fea platform separated from Bann valley ice occupying the Moyola valley lowlands. It then progressively downwasted and backwasted from two lobes, one located in the Broughderg valley to the southwest and the other in the Lissan valley to the southeast. The pattern of ice retreat was thus controlled by the location of local bedrock highs and the direction of ice pressure. The ice finally retreated into the lowland areas south and east of the Sperrin Mountains accompanied by the production of ice marginal and proglacial lakes due to the impounding of meltwater against the rising ground of the mountain range.
