This area extends for 7km north to south from Syonfin to Dromore and west to east from Legamaghery [H457 556] to Altanaveragh [H487 582] and is physiographically contained within the upper Glennamuck Valley. The site comprises outwash spreads, moraines and eskers which cross the valley from south-southwest to north-northeast. The sediments are generally superimposed upon bedrock and are heavily dissected by meltwater. The one main exposure is at Legamaghery where a mainly disused sand pit exposes glaciotectonic clays within a gravel/sand sequence. The exposure (1.5m high by 8m long) is characterised by vaguely stratified interbeds of sorted, clast-supported pebble gravels and medium sand to clay beds. The latter show glaciotectonic deformation and are composed of well-sorted clast-supported granules, and poorly-sorted granule to pebble facies. Gravel units have transitional contacts and up to 25% of erratics are derived from the Tyrone Igneous Complex. The polymodal sand to clay bed (60cm-120cm thick) shows both normal and inverse grading. Deformation styles in this unit include large-scale open fold-type undulations, cm-scale normal and reverse faulting. Large-scale, high angle listric push faulting, lateral elongation or boudinage-type extension of fine-grained lamination are also observed. Soft sediment-style compression of silt/clay units, loading-type displacement of homogenised clay/silt beds, antithetic clay later 'rolling' around less deformable material and zig-zag deformation of the contact between the clay/silt unit and the subjacent gravels also occur.
Sorted gravel and silt beds record deposition in an impounded water body. Sediment deformation means that there is little evidence for depositional direction but it is likely to have been similar to that of later deformation. The strike direction of folds and faults indicates that the glacial re-advance that caused the glaciotectonic deformation, was north to south although this deformation was proglacial rather than subglacial. Sediment deformation style implies that the sediment mass was largely unfrozen and that free water was available.
